zebra: Allow kernel routes to stick around better on interface state changes

zebra: Allow kernel routes to stick around better on interface state changes

Currently kernel routes on system bring up would be `auto-accepted`,
then if an interface went down all kernel and system routes would
be re-evaluated.  There exists situations where a kernel route can
exist but the interface itself is not exactly in a state that is
ready to create a connected route yet.  As such when any interface
goes down in the system all kernel/system routes would be re-evaluated
and then since that interfaces connected route is not in the table yet
the route is matching against a default route( or not at all ) and
is being dropped.

Modify the code such that kernel or system routes just look for interface
being in a good state (up or operative) and accept it.

Broken code:
eva# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure

K>* 0.0.0.0/0 [0/100] via 192.168.119.1, enp39s0, 00:05:08
K>* 1.2.3.5/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 1.2.3.6/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 1.2.3.7/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 1.2.3.8/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 1.2.3.9/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 1.2.3.10/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 1.2.3.11/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 1.2.3.12/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 1.2.3.13/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 1.2.3.14/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 1.2.3.16/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 1.2.3.17/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
C>* 4.5.6.99/32 is directly connected, dummy9, 00:05:08
K>* 4.9.10.11/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:05:08
K>* 10.11.12.13/32 [0/0] via 192.168.119.1, enp39s0, 00:05:08
C>* 192.168.10.0/24 is directly connected, dummy99, 00:05:08
C>* 192.168.119.0/24 is directly connected, enp39s0, 00:05:08
<shutdown a non-related interface>
eva# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure

K>* 0.0.0.0/0 [0/100] via 192.168.119.1, enp39s0, 00:05:28
C>* 4.5.6.99/32 is directly connected, dummy9, 00:05:28
K>* 10.11.12.13/32 [0/0] via 192.168.119.1, enp39s0, 00:05:28
C>* 192.168.10.0/24 is directly connected, dummy99, 00:05:28
C>* 192.168.119.0/24 is directly connected, enp39s0, 00:05:28

Working code:
eva# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure

K>* 0.0.0.0/0 [0/100] via 192.168.119.1, enp39s0, 00:00:04
K>* 1.2.3.5/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 1.2.3.6/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 1.2.3.7/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 1.2.3.8/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 1.2.3.9/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 1.2.3.10/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 1.2.3.11/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 1.2.3.12/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 1.2.3.13/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 1.2.3.14/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 1.2.3.16/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 1.2.3.17/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
C>* 4.5.6.99/32 is directly connected, dummy9, 00:00:04
K>* 4.9.10.11/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:04
K>* 10.11.12.13/32 [0/0] via 192.168.119.1, enp39s0, 00:00:04
C>* 192.168.10.0/24 is directly connected, dummy99, 00:00:04
C>* 192.168.119.0/24 is directly connected, enp39s0, 00:00:04
<shutdown a non-related interface>
eva# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure

K>* 0.0.0.0/0 [0/100] via 192.168.119.1, enp39s0, 00:00:15
K>* 1.2.3.5/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 1.2.3.6/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 1.2.3.7/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 1.2.3.8/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 1.2.3.9/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 1.2.3.10/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 1.2.3.11/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 1.2.3.12/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 1.2.3.13/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 1.2.3.14/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 1.2.3.16/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 1.2.3.17/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
C>* 4.5.6.99/32 is directly connected, dummy9, 00:00:15
K>* 4.9.10.11/32 [0/0] via 172.22.0.44, br-23e378ed7fd2 linkdown, 00:00:15
K>* 10.11.12.13/32 [0/0] via 192.168.119.1, enp39s0, 00:00:15
C>* 192.168.10.0/24 is directly connected, dummy99, 00:00:15
C>* 192.168.119.0/24 is directly connected, enp39s0, 00:00:15
eva#

Signed-off-by: Donald Sharp <sharpd@nvidia.com>