decoder: fix GstVideoCodecFrame flags for interlaced contents.
decoder: fix GstVideoCodecFrame flags for interlaced contents.

Fix support for interlaced contents with GStreamer 0.10. In particular,
propagate GstVaapiSurfaceProxy frame flags to GstVideoCodecFrame flags
correctly.

This is a regression from commit 87e5717.

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