libgfs2: Don't count sentinel dirent as an entry
    
    dir_split_leaf() adds a sentinel dirent using dirent_alloc() which
    increments di_entries in the directory dinode. Since sentinel dirents
    aren't real directory entries, di_entries becomes too high in some
    situations. This patch decrements di_entries after the sentinel dirent
    is created to fix the discrepancy.
    
    rhbz#745161
    
    Signed-off-by: Andrew Price <anprice@redhat.com>