vaapisink: fix get_caps() implementation for GStreamer 1.0.
vaapisink: fix get_caps() implementation for GStreamer 1.0.

Fix GstBaseSink::get_caps() implementation for GStreamer 1.0.X builds
by honouring the filter caps argument. More precisely, this fixes the
following pipeline: gst-launch-1.0 videotestsrc ! vaapisink

https://bugzilla.gnome.org/show_bug.cgi?id=705192

Signed-off-by: Guangxin.Xu <50e7129e8056de7df683c866ddf696a5b52254e7@intel.com>
Signed-off-by: Gwenole Beauchesne <729713629d9640cc095f1c77c692e1881f8093c4@intel.com>

GStreamer/gstreamer-vaapi,gbeauchesne/gstreamer-vaapi,CapOM/gstreamer-vaapi,ceyusa/gstreamer-vaapi,ceyusa/gstreamer-vaapi,CapOM/gstreamer-vaapi,CapOM/gstreamer-vaapi,gbeauchesne/gstreamer-vaapi,gbeauchesne/gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi,GStreamer/gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi