ospfd: Send update for route with new metric

ospfd: Send update for route with new metric

When an AS-external-route is deleted on our system and later added again
with a new metric, then the ospfd would first send a LS-update to remove
the old route and later another LS-update to add the route with the new
metric again.
But when this metric-change happens with no time inbetween the ospfd
recognizes this as the same route and does not send any LS-update.
With the change made here, the ospfd will interpret this route as a
different route, when the metric has changed.

Signed-off-by: Alexander Rose <alexander.rose@secunet.com>