mediawiki::jobrunner -> mediawiki::jobqueue

* Consistent with the principle that things in the module class should describe
  a software stack rather than a role (i.e., 'multimedia' rather than
  'imagescaler')
* Resolves conflicting def'ns for videoscalers resulting from a Puppet parser
  bug that makes class { '::mediawiki::jobrunner' } in
  role::mediawiki::videoscaler resolve to the role class rather than the module
  class.

Change-Id: I70c23114d1737e8d6c22ccc31c84ad3a3e7ac08a