MB-11888: handle missing memcached ssl port

Change-Id: Ib2dea31799272bfee89a49727c9e616365b27ab2
Reviewed-on: http://review.couchbase.org/40450
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>