MB-100: cluster setup for memorysanitytests

- Basetestcase's setup phase to initialize cluster
for memorysanitytests.

Change-Id: I517678f5fcb75058fcdcbf403b299b0454c3f48f
Reviewed-on: http://review.couchbase.org/27320
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: abhinav dangeti <abhinav.dangeti@gmail.com>