master-qa-6335

https://issues.liferay.com/browse/LIFERAYQA-6335

This goes along with:
https://github.com/brianchandotcom/liferay-qa-portal-legacy-ee/pull/3

I wanted to use some of the code from "prepare-test-build" for unzipping legacy liferay bundles for the DB Upgrade tests. I didn't need all of the things that "prepare-test-build" does, so I created a new target called "prepare-test-bundle" that consolidates the repeated code in "prepare-test-build".