Recent change freeze exception - MXs for our domains

[Ricky Zhou]

Hey, we had a @fedoraproject.org mail outage today because Red Hat's MXs
changed IPs.  Previously, we had our MXs set to
mx[123].fedoraproject.org, which pointed to the IPs of the MXes.  With
the last change, we switched to setting the MXs directly to
mx[12].redhat.com, which should always point ot the right place.

Additionally, the change also reenables tummy, telia, and ibiblio, which
we took out for the mass reboot.  

Stephen and Mike +1ed these changes on IRC while we were working on it.

Thanks,
Ricky