check runner instances if they are registered to the coordinator before start the tests

If the runners cannot register themselves to the coordinator somehow, "mvn chop:start" goal should fail. Therefore before tests start, compare the number of total runners with the registered runners to verify all runner instances are registered to the coordinator.  

See also JIRA issue USERGRID-166.
https://issues.apache.org/jira/browse/USERGRID-166

My iCLA is listed under "Salih Kardan"