[JIRA] (OVIRT-1835) Create an automated update mechanism for slaves

Create an automated update mechanism for slaves ----------------------------------------------- Key: OVIRT-1835 URL: https://ovirt-jira.atlassian.net/browse/OVIRT-1835 Project: oVirt - virtualization made easy Issue Type: Improvement Components: Jenkins Slaves Reporter: Barak Korren Assignee: infra Labels: slaves While we already have an automated mechanism for controlling the YUM/DNF repo configuration on slaves, and we also already have a way to install or update components that are critical to the CI system (Both are provided by '{{global-setup.sh}}'), we're lacking a mechanism that can apply general system updates, and more importantly, kernel updates to slaves. Some things we'd like such a mechanism to provide: * Require a minimal amount of manual work (Best case scenario - nothing more then merging a repository update patch would be needed). * Test updated slaves before putting them back to production use * Allow rolling back failed updates