Actually cancel the light alarm.

Cancel the light alarm (with AlarmManager) when it's no longer needed
instead of just setting the expected time to 0.

Bug: 219939849
Test: atest FrameworksMockingServicesTests:DeviceIdleControllerTest
Change-Id: I699eb72c640c8d39736f5f243f4aae9bcd0b4793
1 file changed