Fix ipa-replica-prepare server-cert creation
    
    Fixes an issue introduced in 0a54fac0, we need to specify the current
    master's hostname so that we know to which CA we need to connect to
    create the other's server Server-Cert.
    
    https://pagure.io/freeipa/issue/6755
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>