private Duration expiryTime(Node node) {
        return expiryTime;
    }
Maintenance job which moves inactive nodes to dirty or parked after timeout.

The expiry time is in place to provide a grace period in which nodes can be brought back to active
if they were deactivated in error. As inactive nodes retain their state
they can be brought back to active and correct state faster than a new node.

Nodes with following flags set are not reusable and will be moved to parked
instead of dirty:

- {@link Status#wantToRetire()} (when set by an operator)
- {@link Status#wantToDeprovision()}

@author bratseth
@author mpolden
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/maintenance/InactiveExpirer.java