Don't leak private FAQ titles

Fixes #683

Search results on the client interface for knowledgebase articles would
previous show hits for the internal (private) knowledgebase articles. The
subjects were shown but the articles were not viewable.

This addresses the SQL logic issue causing the private hits to be shown.
Merge pull request #691 from greezybacon/issue/683

Don't leak private FAQ titles

Reviewed-By: Peter Rotich <peter@osticket.com>