vos: refactor code

vos: refactor code

change vos to remove lots of duplicated code for volume deletes and clones

Reviewed-on: http://gerrit.openafs.org/6253
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Alistair Ferguson <alistair.ferguson@mac.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 8d618dceeefacbeb37c4ef3b1f9a8e80552311aa)

Change-Id: I2c26dce796f93c8c993148a94d21dce8608e8c43
Reviewed-on: http://gerrit.openafs.org/6764
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Alistair Ferguson <alistair.ferguson@mac.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>