Change the default for "Allow background activity starts" to off,
matching the logic in the activity manager.
Bug: 129955487
Bug: 129533810
Test: make RunSettingsRoboTests \
ROBOTEST_FILTER=AllowBackgroundActivityStartsPreferenceControllerTest
Change-Id: If9eeae699f9c8b7913da4456a45286f816cc7463
We've modified the implementation to use the value set by DeviceConfig
if the user has not touched the developer options setting (change
fb227077b8652b817a094d37a5215ad7466ee603). We want the Settings screen
to reflect this default until the user explicitly sets it.
Additionally if the user disables developer settings we want to go
back to using whatever DeviceConfig sets.
Bug: 129533810
Test: croot && make RunSettingsRoboTests \
ROBOTEST_FILTER=AllowBackgroundActivityStartsPreferenceControllerTest
Change-Id: I73901a22da928f9a6924b30882b26494cdcd94bc
