CRM-13738 related fix on 'Limit current user' filter handling on Where clause

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* CRM-13738: Activity Report fails if filtering on any contact
  http://issues.civicrm.org/jira/browse/CRM-13738
Merge pull request #2093 from monishdeb/CRM-13738

CRM-13738 related fix on 'Limit current user' filter handling on Where clause