vldb_check: warn about cross-linked mh entries

vldb_check: warn about cross-linked mh entries

Warn if an mh extent entry is referenced by more than one server
number in the IpMappedAddr table.

The serveraddr table is used to determine which server numbers have
IP addresses.  If, for some reason, multiple server numbers
reference the same mh entry, currently, the correct serveraddr value
is calculated only for the lowest server number in the set of server
numbers which reference the same mh entry.  Handle this case, and
warn about the duplicated values in the IpMappedAddr table.

Warn about IpMappedAddr entries which reference non-existent mh
blocks.

Reviewed-on: http://gerrit.openafs.org/7615
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 08e803bce3375bb69a01715b026d844b7a8e0ab3)

Change-Id: I1d2a2d09ed468a247b4da6c07b5ecb4224a80c05
Reviewed-on: http://gerrit.openafs.org/8210
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>