vaapidecodebin ! glimagesink fails performing vaapi postprocessing

Submitted by Matthew Waters @ystreet

Link to original bug (#769253)

Description

With latest gst master with vaapi available/enabled, gst-launch-1.0 playbin uri=blah video-sink=glimagesink results in pipeline failure with:

ERROR vaapipostproc gstvaapipostproc.c:803:gst_vaapipostproc_process_vpp: failed to apply VPP filters (error 2)

Running on an intel chip

Also, vaapidecode doesn't seem to exist anymore by itself so simple testing without vaapipostproc is problematic.