Allow saving duplicate blobs in the repacker

This adds code to the master index to allow saving duplicate blobs
within the repacker. In this mode, only the list of currently in flight
blobs is consulted, and not the index. This correct because while
repacking, a unique list of blobs is saved again to the index.

checker/repacker.go

@@ -136,7 +136,7 @@ func repackBlob(src, dst *repository.Repository, id backend.ID) error {
 		return errors.New("LoadBlob returned wrong data, len() doesn't match")
 	}
 
-	_, err = dst.SaveAndEncrypt(blob.Type, buf, &id)
+	_, err = dst.SaveAndEncrypt(blob.Type, buf, &id, true)
 	if err != nil {
 		return err
 	}