Maintenance on ci.jenkins.io, trusted.ci.jenkins.io and cert.ci.jenkins.io

ci.jenkins.io trusted.ci.jenkins.io cert.ci.jenkins.io

[Final Message] Operation completed successfully:

• Took around 30 minutes as expected.
• A few minor unexpected behaviors are tracked in https://github.com/jenkins-infra/helpdesk/issues/3072 (fixed the 22 of October 2023).

[Initial Message] Monday August 21 2023, starting at 13:45 UTC, the Jenkins controllers ci.jenkins.io, trusted.ci.jenkins.io and cert.ci.jenkins.io will be upgraded to use JDK17 instead of JDK11.

This operation expects 1 or 2 restarts per controller but then should be harmless as we worked on the agent images as per https://github.com/jenkins-infra/helpdesk/issues/3072 and already upgraded 3 other controllers.