fsck.gfs2 pass2: check leaf blocks when fixing hash table
    
    Before this patch, pass2 would attempt to fix the hash table without
    first checking the basic integrity of the leaf blocks it was checking.
    A misplaced leaf might have its entries relocated as a matter of course.
    But if that leaf block had a problem, it could cause all kinds of
    errors, including segfaults. This patch gives the hash table repair
    function the ability to do basic integrity checks on the leaf block,
    and perform repairs if necessary.
    
    rhbz#902920