Don't call ReconcileEngineState on an engine we are trying to stop

Signed-off-by: Eric Weber <eric.weber@suse.com>
(cherry picked from commit 57b4596)

controller/engine_controller.go

@@ -349,7 +349,10 @@ func (ec *EngineController) syncEngine(key string) (err error) {
 		// we allow across monitoring temporarily due to migration case
 		if !ec.isMonitoring(engine) {
 			ec.startMonitoring(engine)
-		} else if engine.Status.ReplicaModeMap != nil {
+		} else if engine.Status.ReplicaModeMap != nil && engine.Spec.DesireState != longhorn.InstanceStateStopped {
+			// If engine.Spec.DesireState == longhorn.InstanceStateStopped, we have likely already issued a command to
+			// shut down the engine. It is potentially dangerous to attempt to communicate with it now, as a new engine
+			// may start using its address.
 			if err := ec.ReconcileEngineState(engine); err != nil {
 				return err
 			}