SUNRPC: Ignore queue transmission errors on successful transmission

If a request transmission fails due to write space or slot unavailability
errors, but the queued task then gets transmitted before it has time to
process the error in call_transmit_status() or call_bc_transmit_status(),
we need to suppress the transmission error code to prevent it from leaking
out of the RPC layer.
Reported-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Tested-by: Chuck Lever <chuck.lever@oracle.com>

net/sunrpc/clnt.c

@@ -2081,8 +2081,8 @@ call_transmit_status(struct rpc_task *task)
 	 * test first.
 	 */
 	if (rpc_task_transmitted(task)) {
-		if (task->tk_status == 0)
-			xprt_request_wait_receive(task);
+		task->tk_status = 0;
+		xprt_request_wait_receive(task);
 		return;
 	}
 
@@ -2167,6 +2167,9 @@ call_bc_transmit_status(struct rpc_task *task)
 {
 	struct rpc_rqst *req = task->tk_rqstp;
 
+	if (rpc_task_transmitted(task))
+		task->tk_status = 0;
+
 	dprint_status(task);
 
 	switch (task->tk_status) {