Fix isSystemUi to avoid System services

We previously switched to checking just status bar permission to
determine whether a service was system UI, but system services also pass
the status bar permissions check, so we still need to retain the
!isCallerSystemOrPhone check.

Bug: 299448097
Test: Flash+build manual test
Flag: ACONFIG android.app.lifetime_extension_refactor STAGING
Change-Id: I8a4304781f4e1bc4f52c9d7b14381d78a8ad5f1d