dirstatemap: also discard item from sets

This seems more consistent to do that. I don't think any test was actually
barking about it, but the code feels a bit more robust now.

Differential Revision: https://phab.mercurial-scm.org/D11332

mercurial/dirstatemap.py

@@ -199,8 +199,12 b' class dirstatemap(object):'
         self._map[f] = new_entry
         if new_entry.dm_nonnormal:
             self.nonnormalset.add(f)
+        else:
+            self.nonnormalset.discard(f)
         if new_entry.dm_otherparent:
             self.otherparentset.add(f)
+        else:
+            self.otherparentset.discard(f)
 
     def reset_state(
         self,