We had been testing the gerrit upgrade from 3.9 to 3.11. Now that we are
running 3.10 we really should test the 3.10 to 3.11 upgrade. Fix that.
While we are at it catch the default test gerrit version up to 3.10 as
well (it was 3.8 but I don't think we use the default anywhere so this
is mostly a noop).
Change-Id: Idafbddf3b9af54b45e6b7e06fda1ede6aa0a995e