ipatests: add test for replica in forward zone
    
    Scenario:
    install a replica with DNS, with the replica part of a forward zone.
    The replica installation should proceed successfully and avoid
    trying to add a DNS record for the replica in the forward zone,
    as the forward zone is not managed by IPA DNS.
    
    Test added to nightly definitions.
    
    Related to https://pagure.io/freeipa/issue/7369
    
    Reviewed-By: Francois Cami <fcami@redhat.com>