CRM-12930 related small fix

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* CRM-12930: CRM/Core/BAO/MessageTemplates.php does not obey CIVICRM_MAIL_SMARTY
  http://issues.civicrm.org/jira/browse/CRM-12930
Merge pull request #1376 from monishdeb/CRM-12930

CRM-12930 related small fix