efl_canvas_vg_container: Initialize alpha color

efl_canvas_vg_container: Initialize alpha color

Summary:
The vg object (container, shape, ...) follows color of VG node data.
The color of node data is not initialized. it can set the required color for each object.
vg container should be layer with an alpha value of 255.

Test Plan: N/A

Reviewers: Hermet, smohanty

Reviewed By: Hermet

Subscribers: cedric, #reviewers, kimcinoo, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D9083

Change-Id: I232ffdb71dd8bb64ca16e30c60016f00c384790d