Arvados

The development of Node Manager went like this:

• First, it immediately paired cloud and Arvados nodes when booting them, to avoid duplicate assignment.
• This didn't prevent duplicate assignments in cases where the cloud node struggled to come up, so we added the assigned_at logic to cover those.
• We added the separate "booted" state to nodes to better handle eventual consistency in the clouds.

Taken together, the logic to immediately pair nodes on boot is not only unnecessary, but causes trouble. A ComputeNodeMonitorActor for a node that doesn't bootstrap correctly may make incorrect shutdown suggestions based on the data in the Arvados node. Taking out the immediate pairing logic will make it easier to identify when a node has failed to bootstrap, and shut it back down appropriately.