DAFS: Ensure logging on attach2 errors

DAFS: Ensure logging on attach2 errors

The attach2 error path transitions a volume to VOL_STATE_ERROR, in
case whatever got us to that error path did not already put the volume
in an appropriate state. Log when we do this, to make sure we do not
end up with a volume in VOL_STATE_ERROR state silently.

Reviewed-on: http://gerrit.openafs.org/6168
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 53230846a202a50f6c3a61b38d62ccba8876f89d)

Change-Id: I4dbe5c6f8be8820620e7a68c7f42b426211dbb82
Reviewed-on: http://gerrit.openafs.org/6324
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>