sdl: Fix block prevention of SDL_WM_GrabInput Consistently check for SDL_APPINPUTFOCUS before trying to grab the input focus. Just checking for SDL_APPACTIVE doesn't work. Moving the check to sdl_grab_start allows for some consolidation. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>