build(deps): bump github.com/containers/storage from 1.15.5 to 1.15.7

Bumps [github.com/containers/storage](https://github.com/containers/storage) from 1.15.5 to 1.15.7.
- [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/v1.15.5...v1.15.7)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>
Signed-off-by: Matthew Heon <mheon@redhat.com>

vendor/github.com/containers/storage/drivers/btrfs/btrfs.go

@@ -627,7 +627,12 @@ func (d *Driver) Remove(id string) error {
 	d.updateQuotaStatus()
 
 	if err := subvolDelete(d.subvolumesDir(), id, d.quotaEnabled); err != nil {
-		return err
+		if d.quotaEnabled {
+			return err
+		}
+		// If quota is not enabled, fallback to rmdir syscall to delete subvolumes.
+		// This would allow unprivileged user to delete their owned subvolumes
+		// in kernel >= 4.18 without user_subvol_rm_alowed mount option.
 	}
 	if err := system.EnsureRemoveAll(dir); err != nil {
 		return err

vendor/github.com/containers/storage/drivers/overlay/overlay.go

@@ -142,8 +142,7 @@ func Init(home string, options graphdriver.Options) (graphdriver.Driver, error)
 	if opts.mountProgram == "" {
 		switch fsMagic {
 		case graphdriver.FsMagicAufs, graphdriver.FsMagicZfs, graphdriver.FsMagicOverlay, graphdriver.FsMagicEcryptfs:
-			logrus.Errorf("'overlay' is not supported over %s", backingFs)
-			return nil, errors.Wrapf(graphdriver.ErrIncompatibleFS, "'overlay' is not supported over %s", backingFs)
+			return nil, errors.Wrapf(graphdriver.ErrIncompatibleFS, "'overlay' is not supported over %s, a mount_program is required", backingFs)
 		}
 	}