subrepo: reset 'self.ui' to the subrepo copy of 'ui' in the hgsubrepo class

Creation of the subrepo's '_repo' object creates a new 'ui' by combining the
parent repo's 'baseui' and reading in the subrepo's hgrc file.  This simply
avoids 'self.ui' and 'self._repo.ui' pointing to different objects, which seems
like a potential source of bugs.

Git and Svn subrepos are unchanged, because they don't have their own ui, and
have always used their parent's for their configuration.

mercurial/subrepo.py

@@ -523,6 +523,7 b' class hgsubrepo(abstractsubrepo):'
         root = r.wjoin(path)
         create = not r.wvfs.exists('%s/.hg' % path)
         self._repo = hg.repository(r.baseui, root, create=create)
+        self.ui = self._repo.ui
         for s, k in [('ui', 'commitsubrepos')]:
             v = r.ui.config(s, k)
             if v: