CBQE-1335 create separate db for storing kv and query latency

Change-Id: I8bd061b40686964b55abe0c2839bd79696e44e5b
Reviewed-on: http://review.couchbase.org/26891
Reviewed-by: Chisheng Hong <chisheng@couchbase.com>
Tested-by: Chisheng Hong <chisheng@couchbase.com>