update agent to use jdk11 and supported Ubuntu LTS

[jtnord]

Given we are telling users to run Java 11 it makes sense we use it for some ATH tests.

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[jtnord]

Update center issue?

Or detached plugins and plugin installation order. Can't see why this worked before and not now unless it is some detached issue and a withPlugin installing something that needs it later.

Need to investigate tomorrow.

master61279|java.io.IOException: Failed to load: JAXB plugin (jaxb 2.3.6-1)
master61279| - Update required: JavaBeans Activation Framework (JAF) API (javax-activation-api 1.2.0-2) to be updated to 1.2.0-3 or higher
master61279|	at hudson.PluginWrapper.

[timja]

I assume related to https://github.com/jenkinsci/jaxb-plugin/releases/tag/jaxb-2.3.6-1 and jenkinsci/jaxb-plugin#23

[jtnord]

Released 8 days ago. The build of the first commit should have failed?