RFR: JDK-8220530: Build compare script does not compare the contents of the test image

[Tim Bell]

Erik:

> This patch adds comparison of the test image, if present in both build
> output directories. I also cleaned away comparing of some old Oracle
> closed images that no longer exist.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8220530
> <https://bugs.openjdk.java.net/browse/JDK-8220530?filter=-1>
>
> Webrev: http://cr.openjdk.java.net/~erikj/8220530/webrev.01/index.html

Looks good to me.

Tim