volinfo: clean up headers

Remove unneeded includes.

Reviewed-on: http://gerrit.openafs.org/5098
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit be152a00a7e4043592094be30f4a811c67a4ac32)

Change-Id: Ieb59affdc63f47d0adb35c89a2fc9d2ea72ba462
Reviewed-on: http://gerrit.openafs.org/11261
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>