CRM-13880 - fix sample data to always set payment_instrument.

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* CRM-13880: Make payment instrument required for all contribution, event registration and membership forms
  http://issues.civicrm.org/jira/browse/CRM-13880
Merge pull request #2164 from davecivicrm/CRM-13880c

CRM-13880 - fix sample data to always set payment_instrument.