[PLG_USER_XUSERS] fix to reference namespaced classes
[PLG_USER_XUSERS] fix to reference namespaced classes

zweidner/hubzero-cms,zooley/hubzero-cms,anthonyfuentes/hubzero-cms,zooley/hubzero-cms,zooley/hubzero-cms,zweidner/hubzero-cms,anthonyfuentes/hubzero-cms,zweidner/hubzero-cms,zweidner/hubzero-cms,zooley/hubzero-cms,anthonyfuentes/hubzero-cms,anthonyfuentes/hubzero-cms