Improve image test and make test run in parallel.

[Random-Liu]

Fixes #241.

This PR:

1. Added images/ directory which contains test images used in CRI validation test. @runcom We can also move your test image to images/. I'll push it to gcr.io/cri-tools for you.
2. Improve image test to make it be able to run in parallel with other tests.

By running test in parallel, it only takes <20s now.

•
Ran 56 of 57 Specs in 18.565 seconds
SUCCESS! -- 56 Passed | 0 Failed | 0 Pending | 1 Skipped 

Signed-off-by: Lantao Liu [email protected]

[runcom]

LGTM but Travis doesn't like the changes

[runcom]

@Random-Liu Travis' failing

[runcom]

ping @Random-Liu @feiskyer

[Random-Liu]

@runcom @feiskyer Fixed the test.

The previous test image I was using is a scratch image with an ENV set.
However, docker returns 0 size for that image, and it fails the size check https://github.com/kubernetes/kubernetes/blob/master/pkg/kubelet/remote/remote_image.go#L88.

I'm not sure whether we should do the check in kubelet. But here I changed the test image to busybox + a file to make the size non-zero.

[Random-Liu]

I think @feiskyer is on vacation. Apply LGTM based on #252 (comment)

[feiskyer]

LGTM