Also import configurations from V2S1 images
Also import configurations from V2S1 images

Since V2S1 image manifests don't include a config blob, when we
initialize a builder using an image with a V2S1 manifest, try to dig
configuration information out of the manifest's layer history, and build
a V2S2 image configuration using the results.

Leave the diffID list unpopulated, because we compute the right values
when we push the image, and to prevent us from mistakes if we ever try
to use them before that in the future.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

Closes: #118
Approved by: rhatdan

ipbabble/buildah,TomSweeneyRedHat/buildah,TomSweeneyRedHat/buildah,nalind/buildah,TomSweeneyRedHat/buildah,rhatdan/buildah,projectatomic/buildah,rhatdan/buildah,nalind/buildah-1,projectatomic/buildah,ipbabble/buildah,projectatomic/buildah,nalind/buildah-1,rhatdan/buildah,nalind/buildah-1,nalind/buildah