Ignore expected exceptions in WhatLinksHere

We are currently loading data by title/namespace, this would
load data from other wiki as well.  (We should add a wiki field
to the loading query, see change I9472361425.)

Bug: 65915
Change-Id: Ic19d4174d3fba2bfc4c3165438bb6a42c64edf52
(cherry picked from commit d4d7ba0d63d4961695af1e7c7e78143cf0abc19b)