Revert cbc49f43e6 because the reasons for hiding non-open games don't
apply or don't apply anymore:
* The filter doesn't actually prevent unwanted clients to join the
server.
* The host can kick or ban unwanted clients now.
* Many users are interested in joining games as observer (either for the
sake of observing or to meet up with buddies).
So for many players the first action after entering the lobby was to
uncheck this checkbox.
Differential Revision: https://code.wildfiregames.com/D218
Reviewed By: mapkoc
This was SVN commit r19619.