CBQE-1100: periodically report kv op latency

Every 10 seconds gather kv op latency (see app/config.py)
latancy collected against 'default' bucket but to be configurable by test-json

Change-Id: Ic68a35bd948c9ff72510f48f1d1fdf9a951e4dc0
Reviewed-on: http://review.couchbase.org/25119
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Chisheng Hong <chisheng@couchbase.com>
CBQE-1098 make bucket creation one of the phases for systest automation

User should assign the number of how many buckets, size, and number of replicas in
the json file for systest automation. Like:
                "1" :
                {
                    "name" : "create_buckets",
                    "desc" :  "create buckets",
                    "buckets" : {"default" : {"quota": "12600", "replicas": "1"},
                                 "sasl": {"count": "2", "quota": "7000", "replicas": "1", "replica_index": "0"}}
                },
This phase exits only if bucket creation finishes

Change-Id: Ibf5c73235575cda1ee5dc0f3ecec25a5f4fa3fb8
Reviewed-on: http://review.couchbase.org/25113
Reviewed-by: Tommie McAfee <tommie@couchbase.com>
Tested-by: buildbot <build@couchbase.com>