remote pull: cancel pull when connection is closed

If a client closes the http connection during image pull, the
service should cancel the pull operation.

[NO TESTS NEEDED] I have no idea how we could test this reliable.

Fixes: containers#7558

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

pkg/api/handlers/libpod/images_pull.go

@@ -85,7 +85,7 @@ func ImagesPull(w http.ResponseWriter, r *http.Request) {
 
 	var pulledImages []*libimage.Image
 	var pullError error
-	runCtx, cancel := context.WithCancel(context.Background())
+	runCtx, cancel := context.WithCancel(r.Context())
 	go func() {
 		defer cancel()
 		pulledImages, pullError = runtime.LibimageRuntime().Pull(runCtx, query.Reference, config.PullPolicyAlways, pullOptions)