CRM-12714 Add is_test to params passed to CRM_Event_BAO_Event::eventTota...

...lSeats to prevent erroneous display of Actual participant count in Find Participants search results summary.

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* CRM-12714: Actual Participants count on Find Participants is mistakenly displayed when search test participant records are present
  http://issues.civicrm.org/jira/browse/CRM-12714