Do not migrate legacy images if snapshots are already present

This commit prevents executing the legacy images migration logic
if snapshotter already finds available snapshots. This mostly
means the migration was already executed and legacy images
had already a chance to be converted into snapshots.

Signed-off-by: David Cassany <dcassany@suse.com>

pkg/snapshotter/loopdevice.go

@@ -543,6 +543,10 @@ func (l *LoopDevice) legacyImageToSnapsot(image string) error {
 			l.cfg.Logger.Errorf("failed setting the snaphsot ID for legacy images: %v", err)
 			return err
 		}
+		if id > 1 {
+			l.cfg.Logger.Debugf("Skipping legacy image migration, there are already snapshots in the system")
+			return nil
+		}
 		l.cfg.Logger.Debugf("Migrating image %s to snapshot %d", image, id)
 
 		snapPath := filepath.Join(l.rootDir, loopDeviceSnapsPath, strconv.FormatInt(int64(id), 10))