volser: Make it clear what's copied from partList

XVolListPartitions uses partList to maintain a list of partition
IDs - it does not use the partFlags field. Make it clear when we
populate the partEntries field that we are only copying the
partition list.

Caught by coverity (#986030)

Reviewed-on: http://gerrit.openafs.org/9262
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 00601179625ffb71461bbcc46629791895cf4793)

Change-Id: I878011efe4baae897e5d4f875c8e02378da38587
Reviewed-on: http://gerrit.openafs.org/9360
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Paul Smeddle <paul.smeddle@gmail.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>