qxl+vnc: register a vm state change handler for dummy spice_server

When qxl + vnc are used, a dummy spice_server is initialized.
The spice_server has to be told when the VM runstate changes,
which is what this patch does.

Without it, from qxl_send_events(), the following error message is shown:
  qxl_send_events: spice-server bug: guest stopped, ignoring

Cc: qemu-stable@nongnu.org
Signed-off-by: Uri Lublin <uril@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

ui/spice-core.c

@@ -732,6 +732,8 @@ int qemu_spice_add_interface(SpiceBaseInstance *sin)
          */
         spice_server = spice_server_new();
         spice_server_init(spice_server, &core_interface);
+        qemu_add_vm_change_state_handler(vm_change_state_handler,
+                                         &spice_server);
     }
 
     return spice_server_add_interface(spice_server, sin);