Fix system settings not cleared when package data is cleared

System settings written by an app were not cleared when app
data was cleared. Apps were thus unable to recover from a bad
state caused by writing a system setting.

BUG: 80134777
Test: Manually tested with test app that writes to system settings.
Verified that the system setting got cleared after clearing app data.

Change-Id: Ibdff885db3e45ea04be845bf06c2d53045115155