Bump github.com/containers/storage from 1.21.0 to 1.21.1

Bumps [github.com/containers/storage](https://github.com/containers/storage) from 1.21.0 to 1.21.1.
- [Release notes](https://github.com/containers/storage/releases)
- [Changelog](https://github.com/containers/storage/blob/master/docs/containers-storage-changes.md)
- [Commits](https://github.com/containers/storage/compare/v1.21.0...v1.21.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>
Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

vendor/github.com/containers/storage/layers.go

@@ -772,7 +772,20 @@ func (r *layerStore) Mounted(id string) (int, error) {
 }
 
 func (r *layerStore) Mount(id string, options drivers.MountOpts) (string, error) {
-	if !r.IsReadWrite() {
+
+	// check whether options include ro option
+	hasReadOnlyOpt := func(opts []string) bool {
+		for _, item := range opts {
+			if item == "ro" {
+				return true
+			}
+		}
+		return false
+	}
+
+	// You are not allowed to mount layers from readonly stores if they
+	// are not mounted read/only.
+	if !r.IsReadWrite() && !hasReadOnlyOpt(options.Options) {
 		return "", errors.Wrapf(ErrStoreIsReadOnly, "not allowed to update mount locations for layers at %q", r.mountspath())
 	}
 	r.mountsLockfile.Lock()
@@ -1000,6 +1013,7 @@ func (r *layerStore) deleteInternal(id string) error {
 		if layer.MountPoint != "" {
 			delete(r.bymount, layer.MountPoint)
 		}
+		r.deleteInDigestMap(id)
 		toDeleteIndex := -1
 		for i, candidate := range r.layers {
 			if candidate.ID == id {
@@ -1031,6 +1045,27 @@ func (r *layerStore) deleteInternal(id string) error {
 	return err
 }
 
+func (r *layerStore) deleteInDigestMap(id string) {
+	for digest, layers := range r.bycompressedsum {
+		for i, layerID := range layers {
+			if layerID == id {
+				layers = append(layers[:i], layers[i+1:]...)
+				r.bycompressedsum[digest] = layers
+				break
+			}
+		}
+	}
+	for digest, layers := range r.byuncompressedsum {
+		for i, layerID := range layers {
+			if layerID == id {
+				layers = append(layers[:i], layers[i+1:]...)
+				r.byuncompressedsum[digest] = layers
+				break
+			}
+		}
+	}
+}
+
 func (r *layerStore) Delete(id string) error {
 	layer, ok := r.lookup(id)
 	if !ok {