CRM-11836 Event Registrant is forced to select a Payment type when there is no fee if pay later enabled

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* CRM-11836: Event Registrant is forced to select a Payment type when there is no fee if pay later enabled
  https://issues.civicrm.org/jira/browse/CRM-11836
Merge pull request #3425 from atif-shaikh/CRM-11836

CRM-11836 Event Registrant is forced to select a Payment type when there...