Comment 0 for bug 1554686

Ironic nodes will be put under maintenance for some reason, for example, temporary BMC offline or unreachable.
Once nodes are put under maintenance, human has to take them out of the state manually, which is unacceptable for large deployment.

Proposal is, when run "_sync_power_states", do not exclude "maintenance" nodes, scan them at longer interval; if "do_sync_power_state" succeeds, flip the "maintenance" status.

This way "maintenance" nodes can get out of "maintenance" without human interference.