Add new unit test cases in WifiNoInternetDialogTest.java
The coverage rate of WifiNoInternetDialog will raise from 10% to 95%
Bug: 151696220
Test: make RunSettingsRoboTests ROBOTEST_FILTER=WifiNoInternetDialogTest
Change-Id: I8256c0adebee9a7f557b467a6ea11cad09e02b33