Replace MEDIA_URL with "local" for thumbnails

MEDIA_URLs contain a domain name and thus have to go through DNS
and possibly a trying-to-be-helpful CDN that blocks urllib2
requests with no User-Agent headers. This change replaces the
MEDIA_URL portion with MEDIA_URL_LOCAL which contains the
(hard-coded!) IP address of the local media server.
use the correct function name for *_url_local functions. oops.
Merge branch 'hotfix-20141024thumbs'