Use port 20891 rather than the reserved 18091

Also clean up port/fd initialization to be more constant for tests

Change-Id: I29dc46e95ef7c4668c8f6759bec9d1404e8560cb
Reviewed-on: http://review.couchbase.org/37690
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>