afs: Move SetupVolume tv initialization after loop

The fields in tv are not used by the loop looking for the given volume
on disk. If we wait until after that loop to initialize the fields in
tv, it is easier to handle errors encountered in the loop.

This should incur no functional change.

Reviewed-on: http://gerrit.openafs.org/9093
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 8f95dc9eb92cb31f9d29eb87daac747f53b5a1cc)

Change-Id: I65f3b647017aebacf28026a648c75b2d279c768e
Reviewed-on: http://gerrit.openafs.org/9130
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>