Add a specific unit test for splitting port with IPv6

The test was copied from greybyte@ccec87c

Signed-off-by: kaiyou <pierre@jaury.eu>

Author: kaiyou

tests/unit/utils_test.py

@@ -552,6 +552,12 @@ def test_split_port_range_with_protocol(self):
         self.assertEqual(external_port,
                          [("127.0.0.1", "1000"), ("127.0.0.1", "1001")])
 
+    def test_split_port_with_ipv6_address(self):
+        internal_port, external_port = split_port(
+            "2001:abcd:ef00::2:1000:2000")
+        self.assertEqual(internal_port, ["2000"])
+        self.assertEqual(external_port, [("2001:abcd:ef00::2", "1000")])
+
     def test_split_port_invalid(self):
         self.assertRaises(ValueError,
                           lambda: split_port("0.0.0.0:1000:2000:tcp"))