aklog: Refactor token acquisition code

aklog: Refactor token acquisition code

This change refactors all of the rxkad specific token acquisition code
out of the common auth_cell loop, and into a number of functions of its
own. There should be no functional changes.

Change-Id: I61314588ba4db6b85db03314d4524322f74c9230
Reviewed-on: http://gerrit.openafs.org/1325
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>