Earlier change to resolve merge conflicts was breaking the current test
because mocked context was used to get wifi manager. Mocking wifi
manager to fix the test and added a check that setWifiEnabled is called
when wifi is not already on.
Test: adb shell am instrument -e class
com.android.server.retaildemo.RetailDemoModeServiceTest -w
com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner
Bug: 31833031
Change-Id: Idd123d50df6ee6db51417645fc877abebe555dc0
cd47cec57d