CBQE-0:Set correct memory quota in case of multiple buckets

Change-Id: If42cdfc9190397e5c90e3ca774698be51fa6f12e
Reviewed-on: http://review.couchbase.org/43395
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Meenakshi Goel <meenakshi.goel@globallogic.com>
Tested-by: Meenakshi Goel <meenakshi.goel@globallogic.com>