Our VrShell use of OpenGL appears to work in an "old" way, something that works on Android, but fails in the UI testapp.

The UI testapp works only if Ozone is configured to use EGL, which presumably is tolerant of this old approach.

The problem (or at least one of them) is that we aren't using VertexAttributeObjects.  cjgrant@ and vollick@ both found that GL errors crop up during draw calls on Linux when not using EGL.  These are found by interlacing calls to query GL error state into our existing calls.