Apologies : bumping Jetty again

[Tom Zeller]

>>Sorry for the churn, I bumped Jetty to 9.1 again, forgetting that
>>breaks the testbed, so I just reverted the parent to 9.0, again.
>
> Does 9.2 break it?

Yes, Jetty version > 9.0 "breaks" the testbed due to dependence on
Servlet 3.1. We could override and downgrade the testbed to Jetty 9.0
and keep parent-v3 current at 9.1+, but we decided to stick with
Servlet 3.0, so it seems parent-v3 should stay compliant with that.