Comment 2 for bug 1045850

Well, my initial thinking when Loic raised this issue was "hey, I don't really know to specify instance zone/subregion in Jenkins". Well, I now see why bug 1003831 got attention. My idea was to re-raise this issue when I'll be on maint. team (next months). But as we now have good usecase for upgrade, let's do it sooner if possible. It will require updating build scripts, and may lead to wave of build breakage (well, we just had one with switch to new EULA handling system).

My initial changes for upgrade can be seen on instance i-1f150379 (may be used as reference, but apparently need to be redone to be sure).