tests: avoid sql queries in TitleTest

testIsAlwaysKnown was invoked on an interwiki link. To have the test
pass, we used addDBData() to inject the interwiki in the database.  This
end up being execute on each test when it is only needed for a single
assertion.

Instead of creating a Title, use Title::makeTitle() to populate the
interwiki, thus letting us avoid the database hits.

Random timing: 1.20s -> 150ms.

Change-Id: I63a4e7b9af5eacb7dc1de4b33b8e631e6c3f1fa6
Merge "tests: avoid sql queries in TitleTest"