volinfo: refactor mode variables

volinfo: refactor mode variables

Untangle the various global mode variables, which became muddled when dsizeOnly
and saveinodes were introduced. DumpInfo now indicates the default mode and
DumpVnodes means print the vnode entries, not scan but sometimes print.  Remove
unused globals.

Reviewed-on: http://gerrit.openafs.org/4735
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 277a8ad658572b60e7e460c945adee78cc04038d)

Change-Id: I9d5d9e9b2b65d703f5b35091f072b31072485d83
Reviewed-on: http://gerrit.openafs.org/11253
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>