ui/gtk: Draw guest frame at refresh cycle

ui/gtk: Draw guest frame at refresh cycle

Draw routine needs to be manually invoked in the next refresh
if there is a scanout blob from the guest. This is to prevent
a situation where there is a scheduled draw event but it won't
happen bacause the window is currently in inactive state
(minimized or tabified). If draw is not done for a long time,
gl_block timeout and/or fence timeout (on the guest) will happen
eventually.

v2: Use gd_gl_area_draw(vc) in gtk-gl-area.c

Suggested-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20240426225059.3871283-1-dongwon.kim@intel.com>
(cherry picked from commit 77bf310084dad38b3a2badf01766c659056f1cf2)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>