lib, bgpd, ospf6d, ospfd, pimd: Allow finish to cleanup a bit more

lib, bgpd, ospf6d, ospfd, pimd: Allow finish to cleanup a bit more

When calling route_map_finish, every place that we do we must
first set the deletion event to NULL, or we will create an infinite
loop, if we are using the delayed route-map application code.
As such we might as well just make the route_map_finish code
do this work, as that there is really no viable alternative here
and route_map_finish should only be called on shutdown.

This fixes an infinite loop in zebra on shutdown when there
are route-maps.

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