ospfd: Discriminate better when selecting links between vertices in SPF

* ospf_spf.c: (ospf_get_next_link) One must check the vertex type, Router or
  Network, to select type link to match against.  Link type 1 has neighbour
  router ID in link_id and link type 2 has IP address of DR.  Since router
  id may have same value as an existing IP address one risks matching a
  router ID against a DR.
1 file changed