Move des/stats.h to rxkad directory

Move des/stats.h to rxkad directory

The structures defined in des/stats.h are rxkad specific, and so
should be handled by an rxkad header file, rather than by something
in the eventually-to-be-removed DES directory.

The structure shouldn't be initialised in libutil. Move initialisation
to rxkad_common, where it is already initialised in the pthread case.

Change-Id: I3de49cfe1752eaa5f273796516e2ff6c289d9533
Reviewed-on: http://gerrit.openafs.org/2576
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>