Unsub list handle (#1097)

* Add list handeling for unsubbing

* fix

* Remove square bracket, causes double listing like mentioned in #1096

* Fix wrong var declaration

Author: swamper123

opcua/common/subscription.py

@@ -300,7 +300,7 @@ def unsubscribe(self, handle):
             return
         params = ua.DeleteMonitoredItemsParameters()
         params.SubscriptionId = self.subscription_id
-        params.MonitoredItemIds = [handle]
+        params.MonitoredItemIds = handles
         results = self.server.delete_monitored_items(params)
         results[0].check()
         with self._lock: