CBQE-0: systest avoid flushq in standalone mode

standalone mode is a quick way to use loader without full infrastructure
(broker/cache/..etc) which means occasional flushing keys to rabbitmq
should be disabled

Change-Id: I79d39f1f79cebfa15b0148ab0648878285f86c23
Reviewed-on: http://review.couchbase.org/40309
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Tommie McAfee <tommie@couchbase.com>