dirstatemap: use the default code to handle "possibly_dirty" case

This case is quite simple too

Differential Revision: https://phab.mercurial-scm.org/D11324

mercurial/dirstatemap.py

@@ -298,8 +298,7 b' class dirstatemap(object):'
             self.addfile(filename, from_p2=True, possibly_dirty=possibly_dirty)
             return
         elif possibly_dirty:
-            self.addfile(filename, possibly_dirty=possibly_dirty)
-            return
+            pass
         elif wc_tracked:
             # this is a "normal" file
             if parentfiledata is None: