ospf6d: restart spf when distance is updated

ospf6d: restart spf when distance is updated

if r1 has a route received from a neighbor and the same route
configured as static, the administrative distance will determine
which route to use

r1(config)# ipv6 route 1:1::1/128 Null0 70

r1# sh ipv6 route
Codes: K - kernel route, C - connected, S - static, R - RIPng,
       O - OSPFv3, I - IS-IS, B - BGP, N - NHRP, T - Table,
       v - VNC, V - VNC-Direct, A - Babel, F - PBR,
       f - OpenFabric,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure

S>* 1:1::1/128 [70/0] unreachable (blackhole), weight 1, 00:00:12
O   1:1::1/128 [110/20] via fe80::1833:c9ff:fe7b:3e43, r1-r2-eth0, weight 1, 00:00:49

The static route is selected. If we now change the administrative distance
in ospf6, the OSPF route should be selected

r1(config)# router ospf6
r1(config-ospf6)# distance 50

r1# sh ipv6 route
Codes: K - kernel route, C - connected, S - static, R - RIPng,
       O - OSPFv3, I - IS-IS, B - BGP, N - NHRP, T - Table,
       v - VNC, V - VNC-Direct, A - Babel, F - PBR,
       f - OpenFabric,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure

S>* 1:1::1/128 [70/0] unreachable (blackhole), weight 1, 00:00:39
O   1:1::1/128 [110/20] via fe80::1833:c9ff:fe7b:3e43, r1-r2-eth0, weight 1, 00:01:16

However the distance is not applied as there are no changes in the routing table

This commit will force the update of the routing table with the new configured distance

r1# sh ipv6 route
Codes: K - kernel route, C - connected, S - static, R - RIPng,
       O - OSPFv3, I - IS-IS, B - BGP, N - NHRP, T - Table,
       v - VNC, V - VNC-Direct, A - Babel, F - PBR,
       f - OpenFabric,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure

O>* 1:1::1/128 [50/20] via fe80::8cb7:e6ff:fef5:2344, r1-r2-eth0, weight 1, 00:00:03
S   1:1::1/128 [70/0] unreachable (blackhole), weight 1, 00:00:19

Signed-off-by: ckishimo <carles.kishimoto@gmail.com>