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>