MB-11888: handle lack of ssl proxy ports in config

Change-Id: I8320fd5b9fef1ceeba19901fc28d45481e71284f
Reviewed-on: http://review.couchbase.org/40449
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>