Fix the cascade protection templatelinks update routine, which apparently has been...

Fix the cascade protection templatelinks update routine, which apparently has been broken since it was introduced, causing it to flood the job queue with refreshLinks job on every parser cache miss:
* Fixed incorrect interpretation of the result of $parserOutput->getTemplates() which led to the array_diff() always being non-empty
* No need to check for $db->select()===false, it throws an exception in that case
* Do a non-recursive update, no need to update links for other pages on a page view