MB-9096: optimized is_node_compatible when cluster is compatible

There's no need to check for particular node's compatibility with
certain feature if entire cluster's mode is new enough.

Change-Id: I9573e6b2049cb00d2adad709ba41ec5285d66a6b
Reviewed-on: http://review.couchbase.org/29317
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Artem Stemkovski <artem@couchbase.com>