DeleteImage(): always delete mapped top layers

When deleting an image, always delete an image's mapped top layers, even
when the unmapped top layer is shared with other images and must
therefore not be deleted.  Mapped top layers aren't shared with other
images, so we never need to preserve them.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

store.go

@@ -2452,6 +2452,10 @@ func (s *store) DeleteImage(id string, commit bool) (layers []string, err error)
 		}
 		layer := image.TopLayer
 		layersToRemoveMap := make(map[string]struct{})
+		layersToRemove = append(layersToRemove, image.MappedTopLayers...)
+		for _, mappedTopLayer := range image.MappedTopLayers {
+			layersToRemoveMap[mappedTopLayer] = struct{}{}
+		}
 		for layer != "" {
 			if rcstore.Exists(layer) {
 				break
@@ -2483,12 +2487,6 @@ func (s *store) DeleteImage(id string, commit bool) (layers []string, err error)
 			if hasChildrenNotBeingRemoved() {
 				break
 			}
-			if layer == image.TopLayer {
-				layersToRemove = append(layersToRemove, image.MappedTopLayers...)
-				for _, mappedTopLayer := range image.MappedTopLayers {
-					layersToRemoveMap[mappedTopLayer] = struct{}{}
-				}
-			}
 			layersToRemove = append(layersToRemove, layer)
 			layersToRemoveMap[layer] = struct{}{}
 			layer = parent

tests/idmaps.bats

@@ -700,11 +700,27 @@ load helpers
 		test $actual = $expected
 	done
 
-	# Remove the containers and image and check that all of the layers we used got removed.
+	# Create a new layer based on the image.
+	run storage --debug=false create-layer --hostuidmap --hostgidmap $lowerlayer
+	echo "$output"
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	upperlayer="$output"
+	run storage --debug=false applydiff -f "$TESTDIR"/layer.empty $upperlayer
+	# Create an image record for the new layer.
+	run storage --debug=false create-image $upperlayer
+	echo "$output"
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	upperimage="$output"
+	echo upperimage:$upperimage
+
+	# Remove the containers and images and check that all of the layers we used got removed.
 	for container in "${containers[@]}" ; do
 		run storage --debug=false delete-container $container
 	done
 	run storage --debug=false delete-image $image
+	run storage --debug=false delete-image $upperimage
 	run storage --debug=false layers
 	echo "$output"
 	[ "$status" -eq 0 ]