delete annotated machines first

In certain circumstances the deleteMachine annotation isn't yet
propagated from the Machine to the AzureMachinePoolMachine. This can
result in deleting the wrong machines. This change ensures the owner
Machine's deleteMachine annotation is always considered and those
machines are deleted first.

Author: mweibel

azure/scope/strategies/machinepool_deployments/machinepool_deployment_strategy.go

@@ -169,6 +169,12 @@ func (rollingUpdateStrategy rollingUpdateStrategy) SelectMachinesToDelete(ctx co
 		"deletingMachines", len(deletingMachines),
 	)
 
+	// if we have machines annotated with delete machine, remove them
+	if len(deleteAnnotatedMachines) > 0 {
+		log.Info("delete annotated machines", "desiredReplicaCount", desiredReplicaCount, "maxUnavailable", maxUnavailable, "deleteAnnotatedMachines", getProviderIDs(deleteAnnotatedMachines))
+		return deleteAnnotatedMachines, nil
+	}
+
 	// if we have failed or deleting machines, remove them
 	if len(failedMachines) > 0 || len(deletingMachines) > 0 {
 		log.Info("failed or deleting machines", "desiredReplicaCount", desiredReplicaCount, "maxUnavailable", maxUnavailable, "failedMachines", getProviderIDs(failedMachines), "deletingMachines", getProviderIDs(deletingMachines))