<oo-diagnostics> modernize and improve

(sync from origin version)
* update necessary RHEL6 selinux-policy version
* remove explicit text references to "service" and "chkconfig"
* stop trying to support Enterprise < 1.2
* remove tests duplicated in oo-accept-systems
* WARN don't FAIL for gear profiles without nodes
* FAIL don't WARN for enterprise RPMs from the wrong source
* don't require "pam_namespace.so no_unmount_on_close" to be strictly at end
* minor refinements to new tests