tests: Add missing socket imports in tests

Type: fix
Change-Id: I646f96517d3bda5c0f5644e6bb89ade7818fc466
Signed-off-by: Tom Jones <thj@freebsd.org>
diff --git a/test/test_ikev2.py b/test/test_ikev2.py
index be788d8..d25b448 100644
--- a/test/test_ikev2.py
+++ b/test/test_ikev2.py
@@ -1,4 +1,5 @@
 import os
+import socket
 import time
 from socket import inet_pton
 from cryptography import x509