qxl: don't render stuff when the vm is stopped.

qxl: don't render stuff when the vm is stopped.

This patch fixes the local qxl renderer to not kick spice-server
in case the vm is stopped.  First it is largely pointless because
we ask spice-server to process all not-yet processed commands when
the vm is stopped, so there isn't much do do anyway.  Second we
avoid triggering an assert in spice-server.

The patch makes sure we still honor redraw requests, even if we don't
ask spice-server for updates.  This is needed to handle displaysurface
changes with a stopped vm correctly.

With this patch applied it is possible to take screen shots (via
screendump monitor command) from a qxl gpu even in case the guest
is stopped.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>