bgpd: Use the default local-preference value and not 0 when adjusting

If we use something like:

route-map x permit 10
 set local-preference +10

We treat that a default is 0, but it's not. We MUST respect the default
BGP local preference value that is set.

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>

Author: ton31337

bgpd/bgp_routemap.c

@@ -2399,6 +2399,7 @@ route_set_local_pref(void *rule, const struct prefix *prefix, void *object)
 	/* Fetch routemap's rule information. */
 	rv = rule;
 	path = object;
+	locpref = path->peer->bgp->default_local_pref;
 
 	/* Set local preference value. */
 	if (path->attr->local_pref)