bgpd: Make bgp ready to remove distinction between 2 nh tracking types

bgpd: Make bgp ready to remove distinction between 2 nh tracking types

Allow bgp to figure out if it cares about address resolution instead
of having zebra care about it.  This will allow the removal of the
zapi type for import checking and just use nexthop resolution.

Effectively we just look up the route being returned and
if it is in either table we just handle it instead of
looking for clues from the zapi message type.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>