Description of problem

As described in RFE-3017, the machine-config ClusterOperator sometimes goes Upgradeable=False on PoolUpdating when new Nodes are added. It should stay Upgradeable=True in that situation, because Nodes adding and leaving an autoscaled cluster is healthy cluster function, and not something that should be waited out (in bursty clusters, it may never stop, and we want folks to be able to update to 4.(y+1) instead of waiting forever).

Version-Release number of selected component

4.8 and later, until MCO-1482 and this ticket tracked a fix landing in 4.19.

How reproducible

Every time.

Steps to Reproduce

1. Install a cluster
2. Scale up a MachineSet's replicas, e.g. oc -n openshift-machine-api scale --replicas 5 machineset.machine.openshift.io $NAME.
3. Watch the machine-config ClusterOperator's Upgradeable, e.g.:

$ oc get -w -o 'jsonpath={.status.conditions[?(@.type == "Upgradeable")]}{"\n"}' clusteroperator machine-config

Actual results

Entries like:

{"lastTransitionTime":"2025-05-20T16:46:59Z","message":"One or more machine config pools are updating, please see `oc get mcp` for further details","reason":"PoolUpdating","status":"False","type":"Upgradeable"}

Expected results

Stays Upgradeable=True the whole time.