Jenkins: Consider using the no-build-test flag

CASSANDRA-16625 and CASSANDRA-18000 added a -Dno-build-test=true flag to skip the dependencies of the Ant test targets. This is useful to speed up the test targets if the build-test target has already been previously run, for example as part of ant jar.

That was created thinking mainly on CircleCI's multiplexer, where we run the same test target repeatedly. Skipping the already run depended on targets can significantly speed up the tests. The flag however is also useful for all other test jobs because every parallel runner can skip the test building step, and we have hundreds of parallel runners. Saving around 30s on every runner adds up considerable savings.

Maybe this flag can also be used for skipping test builds on Jenkins too, so each parallel test split can benefit from a slight boost. That could be done if either build-test or jar have already been run before calling the test target. I'm not familiarized with Jenkins config so I'm not sure whether it makes sense.