Fix for CRM-14354 - Additional gift breaks ARB (auto-renewing) memberships.

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* CRM-14354: Additional gift breaks ARB (auto-renewing) memberships
  https://issues.civicrm.org/jira/browse/CRM-14354
CRM-14354 - Addressed the second manifestation of the bug (when "separate membership payment" is not checked).

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* CRM-14354: Additional gift breaks ARB (auto-renewing) memberships
  https://issues.civicrm.org/jira/browse/CRM-14354
Merge pull request #2973 from GinkgoFJG/CRM-14354v2

Fix for CRM-14354 - Additional gift breaks ARB (auto-renewing) memberships.