client: Handle async errors from xshm setup
client: Handle async errors from xshm setup

XShmAttach can fail asynchronously, so we need to check the
errors in the x error handler during the XSync.

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