The acceptance test harness must restart Jenkins after plugin installation due to the fact that outdated, detached plugins are installed by default. As per this outdated commit, it looks like the intent is just to fix failing tests which have never had to declare detached plugins in their WithPlugins.

One impact of this is that almost every test case must restart Jenkins because it installs updated plugins over the existing detached ones, which prevents dynamic deployment from working.

I think we actually must take the hard path here and fix up the WithPlugins to be accurate.