Resolved issue with Keyspace defined at the cluster level not being set

when the connections are being created. Removed unnecessary concurrency
when defining the keyspace on the connection. Changed the mutex lock
logic in the cluster.addConn to prevent a race condition since when
defining the keyspace there is a recursive call to cluster.addConn.

I added a log.Println(err) to the cluster.changeKeyspace to provide output in the event there is an error.