Don't retain context in locker (#10515)

Use the context for internal timeouts, but disconnect it from outgoing 
calls so we always receive the results and cancel it remotely.

cmd/fs-v1-multipart.go

@@ -714,8 +714,8 @@ func (fs *FSObjects) CompleteMultipartUpload(ctx context.Context, bucket string,
 	}
 
 	// Hold write lock on the object.
-	destLock := fs.NewNSLock(ctx, bucket, object)
-	if err = destLock.GetLock(globalOperationTimeout); err != nil {
+	destLock := fs.NewNSLock(bucket, object)
+	if err = destLock.GetLock(ctx, globalOperationTimeout); err != nil {
 		return oi, err
 	}
 	defer destLock.Unlock()