CBQE-1183 auto rebalance in for local cluster

The json spec will be:
                "7" :
                {
                    "name" : "reb_in_one",
                    "desc" :  "RB-1",
                    "workload" : ["s:3,u:22,g:70,d:3,e:2,m:5,ttl:3000,coq:defaultph1keys,ccq:defaultph2keys,ops:15000",
                                  "b:saslbucket,pwd:password,s:3,u:22,g:70,d:3,e:2,m:5,ttl:3000,coq:saslph1keys,ccq:saslph2keys,ops:15000"],
                    "cluster" :  {"add" : "1"}
                },
And the old hard coded ip format is also supported

Change-Id: I822a9f61ef21e0ec9655fb6531236744b0c10788
Reviewed-on: http://review.couchbase.org/25609
Reviewed-by: Tommie McAfee <tommie@couchbase.com>
Tested-by: buildbot <build@couchbase.com>