Load dogtag RA plugin in installers so profiles can be loaded
    
    In order to call import_included_profiles the dogtag RA plugin
    needs to have been loaded. Modify the requirements to also allow
    the installer context along with the ra_plugin value.
    
    This lets us add missing profiles during a replica installation.
    This is needed for ACME when installing a new replica in a
    cluster of older servers that don't have support for ACME.
    
    https://pagure.io/freeipa/issue/8738
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Mohammad Rizwan <myusuf@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>