Get rid of role::mediawiki::appserver::test

This dates back to when mw1017 was used to test the app server stack on
Precise. The only difference between role::mediawiki::appserver::test and
include role::mediawiki::appserver is the maxclients setting (60 vs. 100),
which isn't usefully testing anything. So chuck it.

Change-Id: I15dd145a13bb4f767a13e101d0e95fef80b3ccfa