treemanifest: remove logic that replaces the stores

Summary:
This was added in D26387205 (ca1249c269) to make the treemanifest store usage look
more like the file store usage, but it appears to cause read-after-write
failures. I'm not sure exactly why, but I think it's because something takes a
reference to the old store and writes to it, then something else reads from the
new store. Or vice versa.

Either way, reverting these three lines fixes it.

Reviewed By: singhsrb

Differential Revision: D26497708

fbshipit-source-id: e9afabed8d5f800260e647d5ed1513eed0bc60cd

eden/scm/edenscm/hgext/treemanifest/__init__.py

@@ -1004,11 +1004,6 @@ class basetreemanifestlog(object):
         else:
             self._mutablesharedpacks.commit()
 
-        if useruststore(self._repo.ui):
-            self.datastore = None
-            self.historystore = None
-            self.makeruststore()
-
     def commitpending(self):
         if not useruststore(self._repo.ui):
             self._mutablelocalpacks.commit()