MB-9518 disallow replication between buckets with different #

.. of vbuckets

Change-Id: I2bd7afda47b31d02029453170368a3c8e460a4b8
Reviewed-on: http://review.couchbase.org/31344
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
MB-9664 disallow xmem replication for clusters with old nodes

1. Unless all the servers in cluster are upgraded to 2.5 the
   new version2 (xmem) should not be available.
2. Check the version of remote cluster, if any remote cluster/node
   is pre-2.2 then version2 should not be allowed.

Change-Id: I503dfc25a67cd4095812d017a8ff3535fc971a2d
[alk@tut.by: simplified get_oldest_node_version]
Signed-off-by: Aliaksey Kandratsenka <alk@tut.by>
Reviewed-on: http://review.couchbase.org/31471
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>