CBQE-1220 enhance the warmup test verification and add test cases

Change-Id: I26c1bd24f3bd6fbe57b0206217968124786f3280
Reviewed-on: http://review.couchbase.org/26174
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Chisheng Hong <chisheng@couchbase.com>
Tested-by: Chisheng Hong <chisheng@couchbase.com>