CRM-14817 - Core CiviCRM - Relationship field mapping option disappear

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* CRM-14817: Relationship field mapping option disappear after select more field
  https://issues.civicrm.org/jira/browse/CRM-14817
Merge pull request #3493 from jimyhuang/CRM-14817

CRM-14817 - Core CiviCRM - Relationship field mapping option disappear