Fix HTTP test by changing port

Author: mthrok

test/torchaudio_unittest/common_utils/case_utils.py

@@ -52,14 +52,15 @@ class HttpServerMixin(TempDirMixin):
     The server is up through the execution of all the test suite defined under the subclass.
     """
     _proc = None
-    _port = 8000
+    _port = 20576
 
     @classmethod
     def setUpClass(cls):
         super().setUpClass()
         cls._proc = subprocess.Popen(
             ['python', '-m', 'http.server', f'{cls._port}'],
-            cwd=cls.get_base_temp_dir())
+            cwd=cls.get_base_temp_dir(),
+            stderr=subprocess.DEVNULL)  # Disable server-side error log because it is confusing
         time.sleep(1.0)
 
     @classmethod