ospf6d: router-id change to display msg to restart

ospf6d: router-id change to display msg to restart

When neighbor state transition from LOADING to
FULL state, active full neighbors count incremented.
The full neighbors count is used for router-id change
if any full neighbor exist, displays message to restart
ospf6/frr to activate new router-id.

In the case of P-t-P neighbor type neighbor transition
from EXCHANGE to FULL which missed full neighbors count.

Ticket:CM-20574
Testing Done:
Initially, Bring up zebra assigned router-id in ospf6
with point-to-point link based neighbor.
Configure static router-id where restart of ospf6 message
is displayed.

Signed-off-by: Chirag Shah <chirag@cumulusnetworks.com>