plugin XEP-0198: Fix disconnecting of component profile:

- There is not need to use stream management with component, so we set mode to `client`
only.
- `_disconnecting_trigger` was causing an exception when disconnecting a component, it is
now disabled in this case.

libervia/backend/plugins/plugin_xep_0198.py

@@ -38,7 +38,7 @@ PLUGIN_INFO = {
     C.PI_NAME: "Stream Management",
     C.PI_IMPORT_NAME: "XEP-0198",
     C.PI_TYPE: "XEP",
-    C.PI_MODES: C.PLUG_MODE_BOTH,
+    C.PI_MODES: [C.PLUG_MODE_CLIENT],
     C.PI_PROTOCOLS: ["XEP-0198"],
     C.PI_DEPENDENCIES: [],
     C.PI_RECOMMENDATIONS: ["XEP-0045", "XEP-0313"],
@@ -202,6 +202,8 @@ class XEP_0198(object):
             return True
 
     def _disconnecting_trigger(self, client):
+        if client.is_component:
+            return True
         session = client._xep_0198_session
         if session.enabled:
             self.send_ack(client)