contint: tweak browsertests URLs

We need browsertests to mimic MediaWiki paths in production. Ie
something like:

    http://localhost:9413/CirrusSearch/wiki/Main_Page
    http://localhost:9413/CirrusSearch/w/api.php

Made possible by having the job create a symlink of w -> .

Jenkins jobs change is: https://gerrit.wikimedia.org/r/115387

Change-Id: I0855e60fb53f68b98beec55e445298a2af22f0fa
Merge "contint: tweak browsertests URLs" into production