vol: remove empty directories left by vos zap -force

vol: remove empty directories left by vos zap -force

The vos zap -force command does not remove the directories associated
with the volume in question (AFS_NAMEI_ENV). When the vos zap -force
command is executed, the volume server goes through the /vicep*/AFSIDat
directories and removes the files associated with the volume id received
as an argument. Unfortunately, the volume server does not remove the
directories associated with this volume. As a result, empty directories
are left behind.

To fix this problem, remove the empty directories left behind when vos
zap -force is executed.

Reviewed-on: https://gerrit.openafs.org/12879
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit 892045a9803ed471986569705d9d727165ca7ecf)

Change-Id: I18b727a561785443f488d60b967182e3ddb9064e
Reviewed-on: https://gerrit.openafs.org/13897
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Marcio Brito Barbosa <mbarbosa@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>