CBQE:2108 Add test to pause only one bucket

Change-Id: I5ab8293c222cc405a41bd0ffb706c2d023fa381d
Reviewed-on: http://review.couchbase.org/35219
Reviewed-by: Aruna Piravi <aruna@couchbase.com>
Tested-by: Aruna Piravi <aruna@couchbase.com>