fsmonitor: update to match new dirstate refactor

The dirstate was refactored so dirstate._map is now at dirstate._map._map. Same
for _copymap, is not _map.copymap. It seems none of the mercurial tests cover
this stuff, but it was caught by our Facebook extension tests.

Differential Revision: https://phab.mercurial-scm.org/D945

hgext/fsmonitor/__init__.py

@@ -251,7 +251,7 b' def overridewalk(orig, self, match, subr'
 
     matchfn = match.matchfn
     matchalways = match.always()
-    dmap = self._map
+    dmap = self._map._map
     nonnormalset = getattr(self, '_nonnormalset', None)
 
     copymap = self._map.copymap