Impala does not properly handle closed catalogd connections.

Filing this issue to raise awareness.

An impalad with an existing (cached) connection to the catalogd will not properly handle that connection being closed from the catalogd side for whatever reason.

Manifestations of this bug:
1. if the catalogd went down or was restarted, such an impalad will crash when trying to run DDL
From the Impala shell you'll see:

Socket error 104: Connection reset by peer

In the error logs:

From the error logs:
terminate called after throwing an instance of 'apache::thrift::transport::TTransportException'
  what():  No more data to read.

2. if the socket times out on the catalogd side, impalads attempting to run DDL can experience an unrecoverable broken pipe

Application Exception : write() send(): Broken pipe