add graphite-related CNAMEs

rationale being: carbon-relay while being technically correct isn't what one
would think about when thinking about graphite (I think).

The -in is to distinguish the fact that this endpoint should be used to send
datapoints to graphite (as opposed to using the api or the web interface).

Change-Id: Id3bc2b4c9fb46742c0d86e22b404f889627f4c92