Try to avoid master queries for GET requests

Try to avoid master queries for GET requests

Skin::getUndeleteLink performs several checks, including a
Title::userCan, which in turn checks the blocked status from master in
order to decide whether to show the link. This happens during GET
requests, and a basic calculation shows that it is responsible for
roughly 15% of the DBPerformance alerts.
This patch rearranges the IF conditions so that the permission check is
performed last, and thus will be avoided if the previous condition is
false.

Change-Id: I45a18a244a26df09beb12e198e0e91a465bd1907