CRM-12562 Mis-named array item check in Batch.php was causing batch upda...

...te to set participant role profile field as is_multiple (conditional on line 204 was checking for participant_role_id instead of participant_role).

----------------------------------------
* CRM-12562: Batch Update Participant Roles Not Set, Not Checkboxes, Data Overwritten
  http://issues.civicrm.org/jira/browse/CRM-12562