storage/lvm: make sure volume cache is refreshed after changes

Even if start/stop fails, still refresh the cache. The failed operation
might still modified something.

qubes/storage/lvm.py

@@ -432,16 +432,18 @@ class ThinVolume(qubes.storage.Volume):
 
 
     def start(self):
+        try:
             if self.snap_on_start or self.save_on_stop:
                 if not self.save_on_stop or not self.is_dirty():
                     self._snapshot()
             else:
                 self._reset()
-
+        finally:
             reset_cache()
         return self
 
     def stop(self):
+        try:
             if self.save_on_stop:
                 self._commit()
             if self.snap_on_start or self.save_on_stop:
@@ -450,6 +452,7 @@ class ThinVolume(qubes.storage.Volume):
             else:
                 cmd = ['remove', self.vid]
                 qubes_lvm(cmd, self.log)
+        finally:
             reset_cache()
         return self