tests: Add missing struct import

Type: fix
Change-Id: I957877d7a82dea437c072e493561894f11321aaf
Signed-off-by: Tom Jones <thj@freebsd.org>
diff --git a/test/test_wireguard.py b/test/test_wireguard.py
index ede02f1..e809dae 100644
--- a/test/test_wireguard.py
+++ b/test/test_wireguard.py
@@ -4,6 +4,7 @@
 import datetime
 import base64
 import os
+import struct
 
 from hashlib import blake2s
 from config import config