Tests: use "return" action in upstream tests.

test/python/delayed/wsgi.py

@@ -11,6 +11,7 @@ def application(environ, start_response):
     write = start_response('200', [('Content-Length', str(len(body)))])
 
     if not body:
+        time.sleep(delay)
         return []
 
     step = int(len(body) / parts)

test/python/upstreams/0/wsgi.py

@@ -1,8 +0,0 @@
-import time
-
-def application(env, start_response):
-    delay = int(env.get('HTTP_X_DELAY', 0))
-
-    start_response('200', [('Content-Length', '0'), ('X-Upstream', '0')])
-    time.sleep(delay)
-    return []

test/python/upstreams/1/wsgi.py

@@ -1,8 +0,0 @@
-import time
-
-def application(env, start_response):
-    delay = int(env.get('HTTP_X_DELAY', 0))
-
-    start_response('200', [('Content-Length', '0'), ('X-Upstream', '1')])
-    time.sleep(delay)
-    return []

test/python/upstreams/2/wsgi.py

@@ -1,8 +0,0 @@
-import time
-
-def application(env, start_response):
-    delay = int(env.get('HTTP_X_DELAY', 0))
-
-    start_response('200', [('Content-Length', '0'), ('X-Upstream', '2')])
-    time.sleep(delay)
-    return []