MB-10329: Make cluster parameters consistent

In older version, we have cluster-init-<param> compared to
cluster-<param>. Now we should prefer cluster-<param> on both
example and help text.

Change-Id: I06bf5d2357b3d9ed49643451bf95ac8688e142b9
Reviewed-on: http://review.couchbase.org/35730
Reviewed-by: Bin Cui <bin.cui@gmail.com>
Tested-by: Bin Cui <bin.cui@gmail.com>