vlserver: Use the right variable for error code in SVL_GetStats

vlserver: Use the right variable for error code in SVL_GetStats

Commit 6c9fe7f80e4b5d9fb21609ee6743470d39dfb8f5 missed one instance
of "code" (as used on the master branch) that should have been changed
to "errorcode" (as used on the 1.6 branch) as part of the cherry-pick.

Fix this so that the right varlue is returned.

This is a 1.6-only change.

Change-Id: I97d9ac5961836843b617bab007d0c4d8bed82fef
Reviewed-on: http://gerrit.openafs.org/11970
Reviewed-by: Daria Phoebe Brashear <shadow@your-file-system.com>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>