aklog: double get_credv5 in retry logic

Fix a bug where get_credv5() is called twice, even if the first one
succeeded, in the aklog retry logic.

(This bug uncovers another bug where get_credv5_akimpersonate
crashes in the krb5 libs when get_credv5 is called back to back.)

Reviewed-on: http://gerrit.openafs.org/11133
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit b9979e1a23ce28b20fe95d5e6042b9b15506c993)

Change-Id: I53b274f5e417ebd2a88b18df15ceb0e1ea39624d
Reviewed-on: http://gerrit.openafs.org/11218
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Perry Ruiter <pruiter@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>