avfvideosrc: video/x-raw(memory:GLMemory) fails to capture video from camera

Submitted by Joe Gorse

Link to original bug (#762645)

Description

The OpenGL caps does not to work on OS X 10.11.3.

Fails with a green screen:
gst-launch-1.0 avfvideosrc ! videoscale ! videoconvert ! "video/x-raw(memory:GLMemory),width=640,height=480" ! glimagesink

Succeeds:
gst-launch-1.0 avfvideosrc ! videoscale ! videoconvert ! "video/x-raw,width=640,height=480" ! glimagesink