Revert "Alter the list of URLs to purge by adding the second domain images are served from"

This reverts commit c4906521f3db2e0ebac15f35af76161826f52010.

Conflicts:

	includes/wikia/Wikia.php
No need to purge all thumb sizes
LocalFilePurgeCacheUrls: pass a reference
Merge pull request #3238 from Wikia/thumbs-purging

No need to purge all thumb sizes