CRM-15455 - avoid creating dupes and using deleted contacts in test
mailings.

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* CRM-15455: email tests do not properly replace tokens
  https://issues.civicrm.org/jira/browse/CRM-15455
Merge pull request #4361 from jmcclelland/civimail-test-duplicate

CRM-15455 - avoid creating dupes and using deleted contacts in test