bpo-40275: Avoid importing socket in test.support (GH-19603)

* Move socket related functions from test.support to socket_helper.
* Import socket, nntplib and urllib.error lazily in transient_internet().
* Remove importing multiprocess.
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index 99e74eb..241ed2c 100644
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -43,6 +43,7 @@
 import tempfile
 from test.support.script_helper import assert_python_ok, assert_python_failure
 from test import support
+from test.support import socket_helper
 import textwrap
 import threading
 import time
@@ -1053,10 +1054,10 @@
 
     def test_basic(self):
         sockmap = {}
-        server = TestSMTPServer((support.HOST, 0), self.process_message, 0.001,
+        server = TestSMTPServer((socket_helper.HOST, 0), self.process_message, 0.001,
                                 sockmap)
         server.start()
-        addr = (support.HOST, server.port)
+        addr = (socket_helper.HOST, server.port)
         h = logging.handlers.SMTPHandler(addr, 'me', 'you', 'Log',
                                          timeout=self.TIMEOUT)
         self.assertEqual(h.toaddrs, ['you'])
@@ -1921,7 +1922,7 @@
         SysLogHandlerTest.tearDown(self)
         support.unlink(self.address)
 
-@unittest.skipUnless(support.IPV6_ENABLED,
+@unittest.skipUnless(socket_helper.IPV6_ENABLED,
                      'IPv6 support required for this test.')
 class IPv6SysLogHandlerTest(SysLogHandlerTest):