zebra: zebra_nhg check each nexthop for active, not just number

zebra: zebra_nhg check each nexthop for active, not just number

We were only checking that two nhg_hash_entry's were equal
based on the active nexthop NUMBER. This is not sufficient in
special cases where whats active with one route using it,
might not be active with the other. We can see this with
routes trying to resolve to themselves.

Ex)

1.1.1.0/24
	-> 1.1.1.1 dummy1 (inactive)
	-> 1.1.1.2 dummy2

1.1.2.0/24
	-> 1.1.1.1 dummy1
	-> 1.1.1.2 dummy1 (inactive)

Without checking each nexthop individually, they will
hash to the same group since they have the same number of
active nexthops.

Fix this by looping over every nexthop for each nhe (they should
be sorted) and checking if the NEXTHOP_FLAG_ACTIVE flag's match.

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