Implemented persistent database connections.

Thanks Anssi Kääriäinen and Karen Tracey for their inputs.

tests/wsgi/tests.py

@@ -2,7 +2,9 @@ from __future__ import unicode_literals
 
 from django.core.exceptions import ImproperlyConfigured
 from django.core.servers.basehttp import get_internal_wsgi_application
+from django.core.signals import request_started
 from django.core.wsgi import get_wsgi_application
+from django.db import close_old_connections
 from django.test import TestCase
 from django.test.client import RequestFactory
 from django.test.utils import override_settings
@@ -12,6 +14,12 @@ from django.utils import six, unittest
 class WSGITest(TestCase):
     urls = "wsgi.urls"
 
+    def setUp(self):
+        request_started.disconnect(close_old_connections)
+
+    def tearDown(self):
+        request_started.connect(close_old_connections)
+
     def test_get_wsgi_application(self):
         """
         Verify that ``get_wsgi_application`` returns a functioning WSGI