vldb_check: fix cross-linked mh entries

vldb_check: fix cross-linked mh entries

When run with -fix, consolidate server numbers in vl entries which
point to the same multi-homed entry. Use the lowest server number
from the set of server numbers which point to the same multi-homed
entry.

Remove unreferenced address entries which are duplicate multi-homed
indexes.

Two passes of vldb_check -fix may be required; first to fix the
vl entry server numbers; then to remove the duplicate address
entries.

Change-Id: I794cec4c176e8aab98a236a9700f58b1269a99bb
Reviewed-on: http://gerrit.openafs.org/7999
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>