Clean up old title on move before reset article id

Calling WikiPage::onArticleDelete without a page_id will reload the
page id, maybe from a (lagged) slave, than the title has the page id
set, and a call to Title::exists return true, which shows the link in
blue and the wrong message.

Bug: 45348
Change-Id: If415dc1729b0bb1cfe7fc75f9e29638a6797d478
Merge "Clean up old title on move before reset article id"