AFSVolClone: remove calls to AssignVolumeName

AFSVolClone: remove calls to AssignVolumeName

The calls in AFSVolClone to AssignVolumeName are unnecessary, because
the volume name is overwritten few lines later with strcpy.

Change-Id: If5031271b9ade08ae248703c8a72f3a083fd4fce
Reviewed-on: http://gerrit.openafs.org/11432
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Daria Brashear <shadow@your-file-system.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>