auth: Refactor afsconf_Open failure handler

Refactor the code which returns a failure from afsconf_Open into
a single section, rather than having multiple copies through out
the routine.

Reviewed-on: http://gerrit.openafs.org/9293
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit a5324a6bb6ff127997c48b54f8ad0e98189f3f1e)

Change-Id: I03f963b717c8095914dd994d7d5612bf57148ce7
Reviewed-on: http://gerrit.openafs.org/11020
Reviewed-by: Perry Ruiter <pruiter@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>