Use Network Manager to configure resolv.conf
    
    IPA used to write a custom /etc/resolv.conf. On Fedora and RHEL,
    NetworkManager is typically maintaining resolv.conf. On reboot or
    restart of the service, NM overwrites the custom settings.
    
    On systems with NM enabled, the DNS server installer now drops a config
    file into NM's global config directory and delegates resolv.conf to NM.
    
    On systems without NM, fall back to create /etc/resolv.conf directly.
    
    Fixes: https://pagure.io/freeipa/issue/7900
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Thomas Woerner <twoerner@redhat.com>