redhat: do not package kauth by default

redhat: do not package kauth by default

Do not package kaserver and related programs by default to discourage
use. Add the '--with kauth' rpmbuild option to allow packagers to
continue include the kauth programs for compatibility.

Change-Id: I8bf9f6dc221afc22ed6c9a33cf101d705e6c4920
Reviewed-on: https://gerrit.openafs.org/12597
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: Benjamin Kaduk <kaduk@mit.edu>