Ensure UPDATE_CONFIG receiver runs only as system user (User 0)

Bug: 406348350
Test: Manually verified the telephony config updated correctlly even
when User10 sends the intent before User0
Flag: EXEMPT bugfix
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:f16bd5890bbbe6596ca2472dbfa8e0ababf59d7e)
Merged-In: I0ddb4ca1b022d0c637c1e2a8948114bbf1b12262
Change-Id: I0ddb4ca1b022d0c637c1e2a8948114bbf1b12262
1 file changed