namei: force-close fd on read or write error

if we errored, just reallyclose so we'll get a new fd

Reviewed-on: http://gerrit.openafs.org/6126
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 730832073a1e87654f28bfff054e24d4170c01dc)

Change-Id: I019b38b6670d3a45b774740d324d5d49e23f94d1
Reviewed-on: http://gerrit.openafs.org/9436
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: BuildBot <buildbot@rampaginggeek.com>