Some changes needed for modifying the system partition
Some changes needed for modifying the system partition

- For P, remount / as rw rather than /system, since /system is now a regular directory, not the mount point of the system partition.

- Set service.adb.root in init before adbd starts (it's not hooked up to make_image_filegroups yet; I'll do that later.)

PiperOrigin-RevId: 193722533

android/android-test,android/android-test,android/android-test,android/android-test,android/android-test