Fix hostname in ping6-ipv6
    
    A host_name in a nagios directive must match one which is defined
    elsewhere in the hosts tree. For this case we needed to use the
    host_name noc02-ipv6.fedoraproject.org to match what was in the ipv6
    namespace.
    
    Signed-off-by: Stephen Smoogen <ssmoogen@redhat.com>