MB-9096: disallow joining any 1.x clusters

Change-Id: I4536322d91c921a9a3b46257ff137ba3e049dd36
Reviewed-on: http://review.couchbase.org/29324
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Artem Stemkovski <artem@couchbase.com>