libadmin: Don't use internal struct for key data

libadmin: Don't use internal struct for key data

The afsconf_dir structure should be regarded as private to the libauth
library, which provides accessors for the commonly used parameters
within it. Rework libadmin so that it uses those accessors when looking
up key data.

Change-Id: I9a623ccadba95622894931ee25319d3bcb019136
Reviewed-on: http://gerrit.openafs.org/3608
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>