salvager: Handle multiple/inconsistent linktables

The ListAFSSubDirs code in namei_ops.c currently detects
incorrectly-named linktable files, and whines about them and says the
salvager will handle them. However, the salvager doesn't really handle
them, since we just use the first linktable we find (FindLinkHandle)
without checking any of the information about it.

So, check for these. Fix FindLinkHandle to only consider a linktable
the "real" linktable to use if it actually matches the volume group id
we're salvaging. Also delete any inconsistent linktables via the new
function CheckDupLinktable later on.

Note that inconsistently-named linktables have been known to have been
created in the past due to a bug in the salvager (fixed by ae227049),
and possibly due to other unknown issues.

Change-Id: Iac461e1254e1f73406a2bc74eaa5a5f53d697304
Reviewed-on: http://gerrit.openafs.org/10322
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: D Brashear <shadow@your-file-system.com>
namei: Ignore misplaced files

The namei salvaging/ListViceInodes code currently ignores files where
we cannot derive an inode number from a given filename. However, if a
file is a valid inode filename, but is in the wrong directory, we
still record it. This can cause the salvager to abort, since it
assumes inode e.g. 12345 is present, but when it tries to open 12345,
namei translates the inode to a nonexistant path, and we bail out.

It is unknown how a namei directory structure can reach this state,
but try to handle it. To be on the safe side, just ignore the files,
and log a message about them. That way, if the files are required for
reconstructing the volume or contain important data, they are still
available if needed. And if they contain incorrect or old data, we
don't screw up the volume by trying to use them.

Thanks to Sabah S. Salih for reporting a related issue.

Change-Id: I529e0c51f48b5b7a62d6aab0470fad71788a5b69
Reviewed-on: http://gerrit.openafs.org/10214
Reviewed-by: D Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>