ospf6d: ospf6 route installation when changed from nssa to regular area.

ospf6d: ospf6 route installation when changed from nssa to regular area.

Problem:
Delay in ospfv3 route installation when area gets converted to regular
from NSSA.

RCA:
when area gets converted from NSSA to normal the type-7(NSSA_LSAs)
gets flushed from the area, as a result the external routes
learnt from these type-7s gets removed. Once the area is moved
to nomral the type 5 lsas needs to flooded through the area
so that routes are re-learnt. however there is a delay in
flooding of these routes until these routes are refreshed.
Due to this there is delay installation of these routes.

Fix:
The Fix involves refreshing of the type 5 lsas once the area
is changed from nssa to regular area.

Signed-off-by: Manoj Naragund <mnaragund@vmware.com>