Make receiver as system user only

- ONSAutoBoot receiver receive LOCKED_BOOT_COMPLETED intent and
  start the OpportunisticNetworkService.
- Avoid receiving LOCKED_BOOT_COMPLETED in guest mode as
  OpportunisticNetworkService is single user and which will not
  start new com.android.phone process

Bug: 304206882
Change-Id: I03afc2ca3fcb9beac10009412d08f31ac6ab5d33
1 file changed