x11: Use _exit rather then exit on X errors (rhbz#680763)
x11: Use _exit rather then exit on X errors (rhbz#680763)

This avoids us trying to restore the original resolution when we're fullscreen
and an X error happens. As restoring fullscreen is a bad idea then as this
involves making more X calls, which can get us stuck (in side an XLockDisplay
call for example).

SPICE/spice,fgouget/spice,freedesktop-unofficial-mirror/spice__spice,alon/spice-server,Fantu/spice,alon/spice-server,alon/spice-server,elmarco/spice,Fantu/spice,fgouget/spice,mathslinux/spice,ya-mouse/spice,mathslinux/spice,fgouget/spice,dezelin/spice,SPICE/spice,mathslinux/spice,ya-mouse/spice,elmarco/spice,elmarco/spice,elmarco/spice,mathslinux/spice,Fantu/spice,dezelin/spice,SPICE/spice,Fantu/spice,freedesktop-unofficial-mirror/spice__spice,elmarco/spice,dezelin/spice,freedesktop-unofficial-mirror/spice__spice,freedesktop-unofficial-mirror/spice__spice,dezelin/spice,dezelin/spice,ya-mouse/spice,freedesktop-unofficial-mirror/spice__spice,alon/spice-server,fgouget/spice,mathslinux/spice,alon/spice-server