hgweb: abstract call to hgwebdir wsgi function

The function names and behavior now matches hgweb. The reason for this
will be obvious in the next patch.

mercurial/hgweb/hgwebdir_mod.py

@@ -217,6 +217,9 class hgwebdir(object):
         return False
 
     def run_wsgi(self, req):
+        return self._runwsgi(req)
+
+    def _runwsgi(self, req):
         try:
             self.refresh()