Fix install permission revocation upon source package uninstallation.

The revocation should only be done when the source package is completely
removed, instead of only being marked as uninstalled for certain users.
However, the original code would erroneously take a null pkg parameter
as the package is gone instead of its original meaning that all packages
need to be updated. So simply drop that parameter and get the pkg from
package manager to see if the package is really being completely
removed.

Bug: 206047992
Test: atest RemovePermissionTest
Change-Id: Iabbf045a87cb00b4c27d562ff126570f385f64c1