MB-9408: ability to change the name of the cluster

Change-Id: I1b21f539d85bbf527b2c97ba500cc7e386ade985
[alk@tut.by: changed config variable name to use underscores instead
of camelcase]
Signed-off-by: Aliaksey Kandratsenka <alk@tut.by>
Reviewed-on: http://review.couchbase.org/34685
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>