volser: Do not reset copyDate in ReClone

When we ReClone in the volserver, do not reset the clone's copyDate to
the current time. If we retain the copyDate between ReClone
operations, then we can know when the clone was first created (and
thus makes local RO clones more consistent with remote RO sites).

Reviewed-on: http://gerrit.openafs.org/3892
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 112b9b35fc701ca26ba7f99c31a73a7a1eecbdc0)

Change-Id: Ifd84a161125bd14799fab2f75f321ca164ef39d2
Reviewed-on: http://gerrit.openafs.org/9451
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: BuildBot <buildbot@rampaginggeek.com>