Hang with readconnroute and persistent connections

The persistent connection code sends a COM_CHANGE_USER to reset the connection state. During the connection reset process, all routed queries are buffered at the backend protocol level. When the connection reset process completes, all queued queries should be routed but it seems that only the first query in the buffer is routed. This means that if more than one query is stored at the protocol level, the client will hang as the query is lost.