This fixes up commit 23b6a66a,
which reimplements election.

  poll raised, retrying
  Traceback (most recent call last):
    ...
    File "neo/client/handlers/master.py", line 41, in notPrimaryMaster
      super(PrimaryNotificationsHandler, self).notPrimaryMaster(*args)
    File "neo/lib/handler.py", line 157, in notPrimaryMaster
      assert primary != self.app.server
    File "neo/client/app.py", line 109, in __getattr__
      return self.__getattribute__(attr)
  AttributeError: 'Application' object has no attribute 'server'