hhvm: make the admin server available on job runners

* Move the include of ::hhvm::admin from ::mediawiki::monitoring::webserver to
  ::mediawiki::hhvm.
* Move the jobrunner fastcgi site from port 9002 to port 9005, so it doesn't
  conflict with the admin site.

Change-Id: I3b3525a7965e7270180f4919a7b031cb72a635ab