TACHYON-71 Prevent Thrift exception from leaking out from MasterClient and WorkerClient classes.

Remove invalid JavaDoc "@throws TException" in method declaration.
Prevent leaking of Thrift exceptions (TException and its inheritance classes) to outside of MasterClient and WorkerClient classes because no
classes outside MasterClient and WorkerClient should know about Thrift services.
Small cleanup to remove empty finally clause in TFsShell class.