cmd: List version in help for commands

List version in help for commands using cmd library

Change-Id: I4da64be11244e64d961e8de47cecb24cbbadce32
Reviewed-on: http://gerrit.openafs.org/10956
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: D Brashear <shadow@your-file-system.com>