status: fix post status invalidation

If the dirstate changed under us, we should throw away what we have a reload it,
should we not ?

mercurial/context.py

@@ -1897,6 +1897,8 b' class workingctx(committablectx):'
                         self._repo.ui.debug(
                             b'skip updating dirstate: identity mismatch\n'
                         )
+                        # throw away anything we have.
+                        dirstate.invalidate()
             except error.LockError:
                 pass
             finally: