[SP-1592] - Backport of BISERVER-12205 - User security gets corrupted (5.2 Suite)

Main discussion thread - http://jira.pentaho.com/browse/ESR-4197
Parent pull request https://github.com/pentaho/pentaho-platform/pull/2145
Added object Authentication into PentahoSession and pulled it in MondrianAbstractPlatformUserRoleMapper.
Unit tests will be soon.

@pentaho-nbaker Nick, I corrected the fix, please review.