Enable ext4 image and disable wic in case of agl-container-guest-demo

Enable ext4 image and disable wic in case of agl-container-guest-demo

In case of AGL IC container integration, this method use
ext4 file system image to create guest rootfs.  It's reusing
wic tools.  In this case, the root filesystem for
container guest must be create  ext4 image.
On the other hand, the wic image build cause long build time.
It does not need in guest image build.

This patch fource enable ext4 image and  fource remove wic at
rootfs image build time.  It's aim to avoid hand operation by
each developer and reduce build time in guest image build.

Bug-AGL: SPEC-4766

Change-Id: I24670dc74c4d88864f43e9aefd2a41f7b0b480b7
Signed-off-by: Naoto Yamaguchi <naoto.yamaguchi@aisin.co.jp>