The ACI needed for staged users and deleted users were granted
only to the uid=admin user. They should rather be granted to
cn=admins group, to make sure that all members of the admins
group are able to call the command ipa user-del --preserve.
This commit also adds integration test for non-regression.
https://pagure.io/freeipa/issue/7342
Reviewed-By: Rob Crittenden <rcritten@redhat.com>
