Updates WebDAV auth hash in password setter

tracim/tracim/controllers/admin/user.py

             password = self.generate_password()
             user.password = password
 
-        user.webdav_left_digest_response_hash = '%s:/:%s' % (email, password)
-
         api.save(user)
 
         # Now add the user to related groups

tracim/tracim/model/auth.py

     def _set_password(self, password):
         """Hash ``password`` on the fly and store its hashed version."""
         self._password = self._hash_password(password)
+        self.update_webdav_digest_auth(password)
 
     def _get_password(self):
         """Return the hashed version of the password."""