CRM-13766 - dont reset scheduled_date, use create function to reset approval fields

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* CRM-13766: civimail with workflow broken: scheduled date not stored with mailing job
  http://issues.civicrm.org/jira/browse/CRM-13766
Merge pull request #2001 from dlobo/CRM-13766

CRM-13766 - dont reset scheduled_date, use create function to reset appr...