viced: Improve CallPreamble error messages

These messages are not very useful right now. At least try to say what
host we sent an error to, so we know which host may be experiencing
some troubles as a result.

Reviewed-on: http://gerrit.openafs.org/9381
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 6c41b1f740e16b5b9adfe9026630595be6f0699e)

Change-Id: I4e9cf5e0d038c572895b4a31bfdff481ea0b3286
Reviewed-on: http://gerrit.openafs.org/10756
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: D Brashear <shadow@your-file-system.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: BuildBot <buildbot@rampaginggeek.com>