fsck.gfs2: re-add a non-allocating repair_leaf to pass1
    
    In an earlier patch, the repair_leaf function was removed from
    pass1. This turns out to cause a problem where there is leaf block
    corruption. This patch adds back in a non-allocating function so
    things work as they used to.
    
    Signed-off-by: Bob Peterson <rpeterso@redhat.com>