zebra: accept bgp remote mac-ip update if the higher-seq-local mac is not bgp-ready

zebra: accept bgp remote mac-ip update if the higher-seq-local mac is not bgp-ready

If a local-MAC or local-neigh is not active locally it is not sent to BGP.
At this point if BGP rxes a remote route it accepts it and installs in
zebra. Zebra was rejecting BGP's update if it had a higher seq local (inactive)
entry. This would result in bgp and zebra falling out of sync.

In some cases zebra would delete the local-inactive entries in sometime (as
a part of the dplane/kernel garbage collection). This would leave zebra
with missing remote entries (which were still present in bgpd).

This change allows lower-seq BGP updates to overwrite zebra's local entry if
that entry happens to be local-inactive.

Note: This logic was already in use for sync-mac-ip updates. Extended the
same logic to remote-mac-ip updates.

Ticket: CM-31626

Signed-off-by: Anuradha Karuppiah <anuradhak@cumulusnetworks.com>