[MESOS-9837] Implement `FutureTracker` class along with helper functions.

• Type: Task
• Status: Resolved
• Priority: Major
• Resolution: Done
• Fix Version/s: 1.9.0
• Component/s: containerization
• Labels: containerization
• Epic Link: debug-endpoint
• Sprint: Containerization: RI-16 Sp 50
• Story Points: 5
• Assignee: Andrei Budnik
• Reporter: Andrei Budnik
• Created: 12/Jun/19 10:53
• Updated: 18/Jul/19 16:19
• Resolved: 18/Jul/19 16:19

Description

Both `track()` and `pending_futures()` helper functions depend on the `FutureTracker` actor.
`FutureTracker` actor must be available globally and there must be only one instance of this actor.