wheezy systems.

[os][rpm] Support CentOS via its own class, stub an OEL
class, small fixes to redhat.pp to be generic enough for use
by these RHEL-ish operating systems, edits to allow EL7-
specific repository inclusions {and exclusions} (jlent)

Add an apt preferences file to use the rsyslog version from
backports.  Remove preferences installation from the syslog
module.

We've switched completely to Kerberized ssh and no longer install
Kerberos rlogin or rsh.

This is the (old) master branch along with the fixes to the
cron file permissions that Russ made.