RiakConnection.receive_code(int) does not read error response off the wire

[broach]

There is a bug in RiakConnection.receive_code(int) that causes it not to read the RpbErrorResp message off the wire.

This leads to a connection being returned to the pool with data still in the input stream, and a subsequent operation will fail due to reading it (potentially causing a huge memory allocation and possible OOM error).