Do not set ca_host when --setup-ca is used
    
    Setting ca_host caused replication failures on DL0
    because it was trying to connect to wrong CA host.
    Trying to avoid corner-case in ipaserver/plugins/dogtag.py
    when api.env.host nor api.env.ca_host had not CA configured
    and there was ca_host set to api.env.ca_host variable.
    
    See: https://pagure.io/freeipa/issue/7566
    Resolves: https://pagure.io/freeipa/issue/7629
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>