zebra: make neigh active when it is modified from local to remote

zebra: make neigh active when it is modified from local to remote

This is a fixup to commit -
f32ea5c07 - zebra: act on kernel notifications for remote neighbors

The original commit handled a race condition between kernel and zebra
that would result in an inconsistent state i.e.
kernel has an offload/remote neigh
zebra has a local neigh

The original commit missed setting the neigh to active when zebra
tried to resolve the inconsistency by modifying the local neigh to
remote neigh on hearing back its own kernel update. Fixed here.

Signed-off-by: Anuradha Karuppiah <anuradhak@cumulusnetworks.com>
Signed-off-by: Vivek Venkatraman <vivek@cumulusnetworks.com>
Ticket: CM-22700