fix upgrade api for DSM 6.1

src/synology_dsm/api/core/upgrade.py

@@ -15,25 +15,27 @@ def __init__(self, dsm):
     def update(self):
         """Updates Upgrade data."""
         raw_data = self._dsm.get(self.API_SERVER_KEY, "check")
-        if raw_data:
+        if raw_data.get("data") and raw_data["data"].get("update"):
+            self._data = raw_data["data"]["update"]
+        elif raw_data.get("data"):
             self._data = raw_data["data"]
 
     @property
     def update_available(self):
         """Gets available update info."""
-        return self._data["update"].get("available")
+        return self._data.get("available")
 
     @property
     def available_version(self):
         """Gets available verion info."""
-        return self._data["update"].get("version")
+        return self._data.get("version")
 
     @property
     def reboot_needed(self):
         """Gets info if reboot is needed."""
-        return self._data["update"].get("reboot")
+        return self._data.get("reboot")
 
     @property
     def service_restarts(self):
         """Gets info if services are restarted."""
-        return self._data["update"].get("restart")
+        return self._data.get("restart")