Use MEDIA_SERIAL on dashboard images.
Review Request #1896 — Created Nov. 7, 2010 and submitted
This is similar to http://reviews.reviewboard.org/r/1887/ and makes sure that all images on the dashboard correctly include MEDIA_SERIAL, which not only makes them cache properly when served with far-future expires headers, but prevents the same images from being fetched twice on the same page with two different URLs.
Checked that all dashboard images now serve with a consistent URL that includes the MEDIA_SERIAL.
Pushed to master as 38b4544. Thanks!