tests/media_storage: add async media parameter

Signed-off-by: Sumner Evans <sumner@beeper.com>

Author: sumnerevans

tests/rest/media/v1/test_media_storage.py

@@ -280,7 +280,13 @@ def _req(
         self.assertEqual(
             self.fetches[0][2], "/_matrix/media/r0/download/" + self.media_id
         )
-        self.assertEqual(self.fetches[0][3], {"allow_remote": "false"})
+        self.assertEqual(
+            self.fetches[0][3],
+            {
+                "allow_remote": "false",
+                "fi.mau.msc2246.max_stall_ms": "20000",
+            },
+        )
 
         headers = {
             b"Content-Length": [b"%d" % (len(self.test_image.data))],