Remove the usage of hidden API and fix the test

- Network class will be inside mainline module, so the external
callers cannot call its hidden API. Remove the usage of hidden
API.
- The orignal test looks wrong because it shouldn't set the data
of intent, it should set the extra of intent instead. (Refer to
the design of ConnectivityService.java) Fix the test and remove
the @Ignore annotation.
- Add 2 new tests to cover the case of receiving unexpected network.

Bug: 182859030
Bug: 183920404
Test: 1. Remove "framework-connectivity.impl"
      2. make RunSettingsRoboTests \
         ROBOTEST_FILTER=WifiNoInternetDialogTest
Change-Id: Ie48a1651629ad9c067728f667cdd91f2f0bccd07