dsn: Don't mark host as having a port if port specified is implicit port

If a host is marked with a special port we only place it inside the
list for that specific protocol. With an implicit port we should place
it inside both lists.

Change-Id: Ie2111bfe49d6491ddbb65920c7e2cb8427726821
Reviewed-on: http://review.couchbase.org/38744
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>