Blender Git Loki

Fix T86956: VSE shading mode ignores Grease Pencil Vertex colors.

Issue is that due to the strange definition of render in grease pencil
(meaning should be rendered similar to rendering). This included normal
viewport rendering in OB_RENDER and OpenGL render in OB_RENDER.

For other rendering modes the overlay vertex opacity would be used. This
patch sets this value to 1 when rendering via a scene strip override.

NOTE: that this isn't a good solution as I expect that users want to use
the opacity of the Grease pencil object. Perhaps the GPencil team has a
better solution for it.