Enforcing Background Check on RESTRICTED apps.

Forcing Background Check for legacy apps (targeting N-) when they're in
the RESTRICTED bucket. For this case, Background Check will only be
enforced when the device is on battery. This means that legacy apps'
services will run as normal while the device is plugged in.

Bug: 145551233
Test: write test app that targets L and confirm service doesn't start
when in RESTRICTED bucket
Change-Id: I25d8d50d062fbd3f7919165027ba411ca4832d4a