VID-2139

Few optimizations and code cleanups in Thumbnail code

https://wikia-inc.atlassian.net/browse/VID-2139

Oh, the reason I gave the thumbs up earlier was b/c I thought you were removing this check to an extension that's been enabled globally, but I actually still see that check here. http://community.wikia.com/wiki/Special:WhereIsExtension?var=1411&searchType=bool&val=1&likeValue=true says it's not set to false anywhere and in common settings it's set to true. We should probably remove it here and from common settings.