libgroup/dlm_controld/gfs_controld: handle zero global_id
    
    bz 493207
    
    groupd can sometimes assign global_id of 0.  dlm_controld and gfs_controld
    now replace 0 id's from groupd with a hash of the group name.  The hash
    function is in libgroup for convenience.
    
    Signed-off-by: David Teigland <teigland@redhat.com>