Remove the pipelining test

HTTP 1.1 pipelining is not used by any major HTTP clients
and the internal state hackery required to make the HTTPCOnnection class
do it was fragile on python 3, making the test flakey

src/calibre/srv/tests/http.py

@@ -271,20 +271,6 @@ class TestHTTP(BaseTest):
 
             server.log.filter_level = orig_level
             conn = server.connect()
-            # Test pipelining
-            responses = []
-            for i in range(10):
-                conn._HTTPConnection__state = http_client._CS_IDLE
-                conn.request('GET', '/%d'%i)
-                if ispy3:
-                    responses.append(conn.response_class(conn.sock, method=conn._method))
-                else:
-                    responses.append(conn.response_class(conn.sock, strict=conn.strict, method=conn._method))
-            for i in range(10):
-                r = responses[i]
-                r.begin()
-                self.ae(r.read(), ('%d' % i).encode('ascii'))
-            conn._HTTPConnection__state = http_client._CS_IDLE
 
             # Test closing
             server.loop.opts.timeout = 10  # ensure socket is not closed because of timeout