remove redundant usercontext, which messes activity form, CRM-13896

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* CRM-13896:
  http://issues.civicrm.org/jira/browse/CRM-13896
CRM-13896, redirect to contact screen is contact is created and action is cancel

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* CRM-13896: Fatal error on cancel action for new activity after new contact is created
  http://issues.civicrm.org/jira/browse/CRM-13896
Merge pull request #2157 from kurund/CRM-13896

remove redundant usercontext, which messes activity form, CRM-13896