build tsalvaged, tvolser, and dvolser targets on *nbsd*

Reviewed-on: http://gerrit.openafs.org/5595
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 1ca207f18491147bb7f7de3e588fb1979ac3d0c5)

Change-Id: I8570370905fa4c3bbdd72f5535329cfab5bebf1a
Reviewed-on: http://gerrit.openafs.org/10121
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: Jonathan A. Kollasch <jakllsch@kollasch.net>
Reviewed-by: Jonathan A. Kollasch <jakllsch@kollasch.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>