Show error tips if load hive error occurs and can not be connected.

"Load Hive Table From Tree" page always show "Loading Databases" without error tips, when hive error occurs and can not be connected.

2017-06-07 14:59:08,419 ERROR [http-bio-7070-exec-5] controller.TableController:181 : Could not connect to meta store using any of the URIs provided. Most recent failure: org.apache.thrift.transport.TTransportException: java.net.ConnectException: Connection refused