* (bug 21026) Fixed file redirects on shared repos on non-English client wikis

* (bug 21026) Fixed file redirects on shared repos on non-English client wikis
memcached key name for image redirect info caching was including the local wiki's namespace translations, so non-English client sites that cached negative lookups didn't get them cleared when the redirect entry is updated from the master site. The negative lookup would continue to be used until it expired, leading to confusing brokenness.
Changed the cache keys to use the bare name, since we only care about NS_FILE cases we can tack it back on to the title after we load it up.