vol: use correct file name base for temporary file

vol: use correct file name base for temporary file

Inconsistent use of temporary file name bases resulted in
the temporary files never being deleted.

Reviewed-on: http://gerrit.openafs.org/3705
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 01fc5d0577409c889ca5ad6f3bc1d624138922bc)

Change-Id: Ia66d30fec2633bc2fbb8a6fcc5fd42a9fc9cace0
Reviewed-on: http://gerrit.openafs.org/3852
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>