[outages] Comcast public-facing DNS servers unreachable

[Paul Ebersman]

outages> This affects comcast.com, xfinity.com, and xfinity.net as well
outages> as comcast.net as I originally reported.  Unsure of any other
outages> domains.

Comcast does it's own auth for any of it's direct services, so all
domains related to those. nbcuniversal.com is on akamai, so unaffected.

the DNS team used to monitor @comcastdns on twitter, not sure if that's
still the case.