tunneling: Reduce priority of multicast tunnels.

tunneling: Reduce priority of multicast tunnels.

It's possible to have an incoming packet that matches both a unicast
and multicast tunnel if the source address corresponds to the remote_ip
of a unicast tunnel and the destination is multicast.  Currently this
will match the multicast tunnel but in reality the unicast tunnel
should probably be considered more specific.  This is actually a
common situation in protocols that use a combination of multicast
for flooding and unicast for responses.

Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>