zebra: mark connected nh inactive if not matching ifindex

zebra: mark connected nh inactive if not matching ifindex

If we are asked to check if a nexthop is active and it matches a
connected route but the ifindex on it does not match the interface
with the connected route, mark as inactive. This is a bad nexthop.

Before, we would skip this check and just assume any nexthop that matches
on a connected route is valid and return here then fail during
installation. This adds a check for the IPV*_ifindex nexthop case where the
ifindex we have been sent doesn't match.

Old:
F>r 0.0.0.0/0 [200/0] via 20.0.0.2, test, weight 1, 00:00:27
  r                   via 40.4.4.4, lo, weight 1, 00:00:27

New:
F>* 0.0.0.0/0 [200/0] via 20.0.0.2, test, weight 1, 00:00:06
  *                   via 40.4.4.4, lo inactive, weight 1, 00:00:06

Signed-off-by: Stephen Worley <sworley@cumulusnetworks.com>