Correct the permission check for the Keystore maintenance method
that returns the list of app UIDs which have keys that are
bound to a specific SID.
The previous check relied on SELinux policies. But the Settings
app that calls this method has a permission - MANAGE_USERS -
that is more appropriate to check.
Bug: 302109605
Test: Manual.
Change-Id: Ia26256cf995d16d03d0bb92d8b237f7bbea30d07