Using closed connection in the protobuf client

[dgnorton]

If the remote server closed the connection, the protobuf client will constantly print this error message in the log when it should just drop the connection and wait for the remote server to reconnect:

[EROR] (github.com/influxdb/influxdb/coordinator.(*ProtobufClient).readResponses:174) Error while reading messsage size: &{%!d(string=use of closed network connection)}

[dgnorton]

In case anyone else has the same thought I had at first, that it should check for errorClosing, here is a discussion on the topic https://code.google.com/p/go/issues/detail?id=4373.