Update expiry of fixture certs to at least 2 years in the future

[cyli]

Signed-off-by: Ying Li ying.li@docker.com

[riyazdf]

LGTM on green!

[cyli]

Updated this to do another 3 things:

1. use a sha256 signing algorithm instead of whatever is default (which may be SHA1 on older versions of openssl, which we reject)
2. use a different CN for the intermediate cert so we can more easily tell what signed what
3. also generate 2 other certs that are in the fixtures library

[riyazdf]

thanks for the updates! LGTM pending CI :)

[endophage]

LGTM