volser: set error, not code, before rfail

volser: set error, not code, before rfail

The rfail cleanup handler overwrites 'code' ~unconditionally, but
does use an existing 'error' value if present.  Since the intent
is to return failure to the caller, preserve the code in the error
variable and do so.

FIXES 131897

Reviewed-on: http://gerrit.openafs.org/12108
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 888fc16db5f0063464bf219a6cf6fee0faea4705)

Change-Id: Ic8aab7cbe9bac6c0677b1e3bc2ca2b59a76bd621
Reviewed-on: https://gerrit.openafs.org/12126
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>