aix: link afs_dynamic_kerbauth to rfc3961

Change-Id: Ie06fc83382e18f2e90a5f3874a8bb71afa0c4748
Reviewed-on: http://gerrit.openafs.org/10106
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>