[JIRA] (OVIRT-2254) Create slave borrowing flow

Create slave borrowing flow --------------------------- Key: OVIRT-2254 URL: https://ovirt-jira.atlassian.net/browse/OVIRT-2254 Project: oVirt - virtualization made easy Issue Type: New Feature Components: Jenkins Master, Jenkins Slaves Reporter: Barak Korren Assignee: infra Create a set of jobs and groovy functions that will enable one Jenkins master to borrow slaves from another Jenkins master. h3. Acceptance criteria # We define a borrower and a borrowing Jenkins instances. Ans support the use case where both are the same instance # Borrowing is done by setting up a JNLP connection from the slave of the borrower instance to to borrowing instance. # On the borrower instance: ## We have a "borrow" job that: ##* Takes slave requirement details, allocates a matching slaves and make it connect via JNLP to the borrowing instance ##* If all matching slaves are already borrowed by other instances, try to call the garbage collector jobs (see below) on borrowing instances to free the slaves. ## We have a "return" job that is called by a borrowing instance to return a slave # On the borrowing instance ## STDCI tries to borrow slaves from a predefined instance if not matching slaves are available locally ## Once borrowed - slaves stay attached to the borrowing instance so they can be reused by other STDCI jobs. ## We have a "garbage collector" job that is triggered periodically or by the borrower instance. It looks at borrowed slaves, and frees ones that were not used recently.