ConnectivityServiceTest is a unit test and must never read
actual flag values from the device, because:
- If it did, its results would not be reproducible.
- At least on S and T, reading flags from device fails because
the test lacks the READ_DEVICE_CONFIG permission.
Instead, throw a clear exception if ConnectivityService checks a
feature flag that is not explicitly set in the test.
Test: test-only change
Change-Id: Ic3855ffa944f170f5fda9c3456776f5e1f2ef388
2322bc04cb