gfs_controld: read lockless resources from ckpts
    
    bz 474163
    
    When we mount and read plock state from a checkpoint, we can't
    ignore zero-size checkpoint sections, because we need to add
    the resource along with its owner from the section id.  What
    should be skipped are zero-length section id's.
    
    Signed-off-by: David Teigland <teigland@redhat.com>