Clair integration

[liangchenye]

Signed-off-by: liangchenye liangchenye@huawei.com

Works in my test: add put/get interface to scan docker v2 image.

TODO:

1. we need to add a specific clair upstream version to 'Godeps'
2. take to @ChengTiesheng about the integrate with his work.

And there will be other patches to support:

1. v1 image
2. aci image

[liangchenye]

@MabinGo Godeps & channel are all added, works in my test :)

Discussed with tiesheng, we decide to keep the two functions separated.

[philips]

FYI @Quentin-M

[MabinGo]

@liangchenye Thanks, LGTM