Backport yum package body from 3.6 cfe packages.cf

- tested on RHEL6.5 x86_64 cfe 3.5.2
The ``$(redhat_knowledge.check_update_postproc)`` variable does not appear in this 3.5 version of ``packages.cf``. I assume it is a copy paste error from the 3.6/3.7 version.