Testing: Fix test_no_connection_exception

... when another CrateDB is running on the default port 4200.

src/crate/client/test_http.py

@@ -127,7 +127,7 @@ def test_connection_reset_exception(self):
             client.close()
 
     def test_no_connection_exception(self):
-        client = Client()
+        client = Client(servers="localhost:9999")
         self.assertRaises(ConnectionError, client.sql, 'select foo')
         client.close()