remove global shared test cluster

In my experiments, this doesnt really buy much, but it causes reproducibility grief, and prevents things like leak detection from working (I would like to do more e.g. with the filesystem).

master:
[INFO] Execution time total: 5 minutes 51 seconds
[INFO] Tests summary: 672 suites, 4412 tests, 478 errors, 51 ignored (49 assumptions)

patch:
[INFO] Execution time total: 6 minutes 40 seconds
[INFO] Tests summary: 672 suites, 4412 tests, 479 errors, 51 ignored (49 assumptions)

So the savings is really not much in the scheme of things: I think reproducibility is better.