salvager: Error volumes on GetInodeSummary errors

When GetInodeSummary fails due to an internal failure (not from just
failing to find applicable inodes), currently it just returns an
error, and does not return the checked-out singleVolumeNumber back to
the fileserver.

When we fail to gather inodes, we should force the volume to an error
state, since we haven't salvaged the volume. But if we fail to find
any applicable inodes, we just want to VOL_DONE the volume, since the
header has possibly been destroyed, and the volume doesn't exist.

So, issue an FSYNC_VOL_FORCE_ERROR command when we encounter errors in
GetInodeSummary, except when we fail to find applicable inodes.

Reviewed-on: http://gerrit.openafs.org/4439
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 8084fc28a3069949bdc788f048fa8a96c012b96d)

Change-Id: I64e8e1ac8e3386d09a3bcd7696a2d0f70ded33b0
Reviewed-on: http://gerrit.openafs.org/9459
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>