Don't run headless test on linux
Don't run headless test on linux

mitchmindtree/glutin,tomaka/glutin,bvssvni/glutin,mmatyas/glutin,ozkriff/glutin,tomaka/winit,mbrubeck/glutin,ecoal95/glutin,notriddle/glutin,servo/glutin,vberger/glutin,mbrubeck/glutin,nc4rrillo/glutin