Fix incorrect order of cleanup on exit.
Fix incorrect order of cleanup on exit.

Fixes random exceptions thrown in SwapBuffers due to BaseGame being disposed before threads had actually been stopped.

paparony03/osu-framework,Nabile-Rahmani/osu-framework,default0/osu-framework,ZLima12/osu-framework,DrabWeb/osu-framework,Nabile-Rahmani/osu-framework,ppy/osu-framework,peppy/osu-framework,Tom94/osu-framework,default0/osu-framework,EVAST9919/osu-framework,peppy/osu-framework,naoey/osu-framework,ZLima12/osu-framework,Tom94/osu-framework,smoogipooo/osu-framework,naoey/osu-framework,ppy/osu-framework,EVAST9919/osu-framework,ppy/osu-framework,RedNesto/osu-framework,DrabWeb/osu-framework,EVAST9919/osu-framework,peppy/osu-framework,paparony03/osu-framework,EVAST9919/osu-framework,smoogipooo/osu-framework,DrabWeb/osu-framework,RedNesto/osu-framework