Add tests for ipa-cacert-manage delete command
    
    This tests the following cases:
    - deletion without nickname (expect fail)
    - deletion with an unknown nickname (expect fail)
    - deletion of IPA CA (expect fail)
    - deletion of a root CA needed by a subCA (expect fail)
    - deletion of a root CA needed by a subCA with --force (ok)
    - deletion of a subca (ok)
    
    As a side-effect this also tests install by installing the LE
    root and a sub-ca. The sub-ca expires in 2021 but I tested in
    the future the ipa-cacert-manage install doesn't do date
    validation so for now this is ok.
    
    https://pagure.io/freeipa/issue/8124
    
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>