Fix rare race condition with missing ccache file
    
    In some circumstances the ccache file may disappear while
    mod_auth_gssapi still has a valid cookie and the client is performing a
    json server call.
    
    This may lead to credentials getting sourced from the keytab.
    Make sure we enforce what GSS NAME we want to resolve so HTTP creds are
    never mistakenly sourced.
    
    Ticket: #6972
    
    Signed-off-by: Simo Sorce <simo@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>