NettyRpcServer may hange if it should skip initial sasl handshake

NettyRpcServer may hange if it should skip initial sasl handshake when server does not enable security and client enables security, I think this problem is caused by two reasons：

• For Server:
  The type of the response is RpcResponse, but for NettyRpcServerPreambleHandler,when it send RpcResponse ,NettyRpcServerResponseEncoder does not exist, so RpcResponse messages cannot be sent.

• For Client
  When NettyHBaseSaslRpcClientHandler receives SaslUtil.SWITCH_TO_SIMPLE_AUTH, it does not remove SaslChallengeDecoder and NettyHBaseSaslRpcClientHandler, so the latter responses are considered to be incorrect.