Revert "Revert "Enable JPG thumbnail chaining on all wikis except commons""

This reverts commit 3c587287fb833495fb15c305ac08edcc679f4192.

Change-Id: I236af6b26bc0624e8cc02f43831ad5e043baa2ba
Merge "Revert "Revert "Enable JPG thumbnail chaining on all wikis except commons"""