subrepo: subrepo isolation, pass baseui when cloning a new subrepo (issue2904)

Create the repo with baseui because it should only get the global configuration.

After this patch issue2904 is finally fixed.

mercurial/subrepo.py

@@ -507,7 +507,7 b' class hgsubrepo(abstractsubrepo):'
                                      % (subrelpath(self), srcurl))
                 parentrepo = self._repo._subparent
                 shutil.rmtree(self._repo.path)
-                other, cloned = hg.clone(self._repo._subparent.ui, {},
+                other, cloned = hg.clone(self._repo._subparent.baseui, {},
                                          other, self._repo.root,
                                          update=False)
                 self._repo = cloned.local()