Prevent inheritKeyStoreKeys from taking effect on system UID apps

When an app that used to share UID with system decided to leave shared
UID, it should not be allowed to inherit all keys from its previous UID
as that will nuke all system UID keys, breaking critical system
functionality.

Test: manual
Bug: 216560195
Change-Id: I27eea398b7c2ec624f1239aee72755cfb8d50339