vldb_check: rebuild free list with -fix

vldb_check: rebuild free list with -fix

Rebuild the vldb free chain in addition to the hash chains when
vldb_check is run with the -fix option.  Print a FIX: message for
entries added to the free chain.

Example vldb with a broken free chain.

    $ vldb_check vldb.broken
    address 199364 (offset 0x30b04): Free vlentry not on free chain
    address 223192 (offset 0x36818): Free vlentry not on free chain
    address 235180 (offset 0x396ec): Free vlentry not on free chain
    Scanning 1707 entries for possible repairs

    $ vldb_check -fix vldb.broken
    Rebuilding 1707 entries
    FIX: Putting free entry on the free chain: addr=199364 (offset 0x30b04)
    FIX: Putting free entry on the free chain: addr=223192 (offset 0x36818)
    FIX: Putting free entry on the free chain: addr=235180 (offset 0x396ec)

Thanks to Kostas Liakakis for reporting this bug.

Reviewed-on: http://gerrit.openafs.org/11598
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 3b9d52b2e8020cce65d55516db36580d58a51f0b)

Change-Id: I01987451857b26fb9e87984da85976196145e1dd
Reviewed-on: http://gerrit.openafs.org/12084
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>