zebra: zebra2proto() handle kernel/connect type

zebra: zebra2proto() handle kernel/connect type

When dplane_fpm_nl is used the "Please add this protocol(n) to proper
rt_netlink.c handling" debug message is emitted for any route of type
kernel or connected.

This severely reduces performance of dplane_fpm_nl when large numbers
of these routes are present in the RIB.

The messages are not observed when using the original fpm module since
this uses a custom function, netlink_proto_from_route_type().

zebra2proto() now returns RTPROT_KERNEL for ZEBRA_ROUTE_CONNECT and
ZEBRA_ROUTE_KERNEL. This should only impact dplane_fpm_nl's use of
the common netlink routines since these routes generally ignored via
checking of RSYSTEM_ROUTE().

Signed-off-by: Duncan Eastoe <duncan.eastoe@att.com>