fsck.gfs2: Check the integrity of the journal index
    
    This patch checks the jindex system directory to make sure the entries
    all start with "journal" and so forth. If not, the jindex is deleted
    and rebuilt. As part of this patch, I moved where we read in the rindex
    file and rgrps to an earlier point in time, before the journals are
    replayed. This allows us to remove a dummied-up rgrp kludge in the code.
    However, if the replayed journal block is part of an rgrp, we need to
    refresh the rgrp based on the values rewritten from the journal.