CRM-13225 related fix for Membership Import during update

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* CRM-13225: Activity/Participant/Membership import is broken due to import resturcturing
  http://issues.civicrm.org/jira/browse/CRM-13225
Merge pull request #1460 from monishdeb/CRM-13225-QA-fix

CRM-13225 related fix for Membership Import during update