Do not leak whether package exists in revokeOwnPermissionsOnKill

Previously, a direct call to the PermissionManagerService API would
reveal if the target package uid is -1 (package not installed) or >0

Bug: 219739967
Test: None, this is a string update
Change-Id: Ifbe5a30330d5569ed301d23d88989bb3a094bb97
Merged-In: Ifbe5a30330d5569ed301d23d88989bb3a094bb97