grpc: don't tear down the shared master connection on a caller's own timeout (#9775)

A Canceled/DeadlineExceeded from the caller's per-request context was
treated like a dead channel: it closed the shared cached ClientConn and
cancelled every other in-flight RPC on it with "the client connection is
closing". Under a burst of concurrent chunk assigns (e.g. a large S3
multipart upload) one slow assign hitting its 10s attempt timeout could
poison the connection for all the rest, cascading into a flood of 500s.

Thread the caller's context into shouldInvalidateConnection and only
invalidate on Canceled/DeadlineExceeded while that context is still live,
which isolates the genuine stale-channel signal (a peer restart behind a
k8s Service VIP). To carry the context, add a ctx parameter to the
existing WithGrpcClient, WithMasterClient, and WithMasterServerClient; the
master assign and volume-lookup paths pass their per-attempt context and
every other caller passes context.Background().

weed/command/upload.go

@@ -145,7 +145,7 @@ func runUpload(cmd *Command, args []string) bool {
 }
 
 func readMasterConfiguration(grpcDialOption grpc.DialOption, masterAddress pb.ServerAddress) (replication string, err error) {
-	err = pb.WithMasterClient(false, masterAddress, grpcDialOption, false, func(client master_pb.SeaweedClient) error {
+	err = pb.WithMasterClient(context.Background(), false, masterAddress, grpcDialOption, false, func(client master_pb.SeaweedClient) error {
 		resp, err := client.GetMasterConfiguration(context.Background(), &master_pb.GetMasterConfigurationRequest{})
 		if err != nil {
 			return fmt.Errorf("get master %s configuration: %v", masterAddress, err)