storage/reflink: delete all images at beginning of create()

Ensure that there are no leftover image files for the volume, e.g. from
an unsuccessful removal of a previous incarnation of this vid, or from
an messily restored pool filesystem backup. We don't want to preserve
any stale data (revisions) or metadata (size) in the new incarnation.

qubes/storage/reflink.py

@@ -154,6 +154,7 @@ class ReflinkVolume(qubes.storage.Volume):
     @_coroutinized
     @_locked
     def create(self):
+        self._remove_all_images()
         if self.save_on_stop and not self.snap_on_start:
             _create_sparse_file(self._path_clean, self._get_size())
         return self