fix error namespace for ComponentXMPP

in SlixTest, if mode=="component", restore
jabber:client namespace afterwards

Fixes #3476
Fixes #3474

tests/test_stream_xep_0385.py

@@ -14,9 +14,6 @@ class TestSIMS(SlixTest):
             mode="component", jid="whatevs.shakespeare.lit", plugins={"xep_0385"}
         )
 
-    def tearDown(self):
-        self.stream_close()
-
     def test_set_file(self):
         with NamedTemporaryFile("wb+") as f:
             n = 10