Fix urlutils tests on Qt 5.6.1

For some reason the behaviour of QHostAddress("31c3").isValid() changed
with Qt 5.6.1: https://bugreports.qt.io/browse/QTBUG-53983

This causes the test to fail because Qt thinks this is a valid IP, so we
think it's a valid URL.

tests/unit/utils/test_urlutils.py

@@ -336,7 +336,9 @@ def test_get_search_url_invalid(urlutils_config_stub, url):
     (False, True, False, '23.42'),  # no DNS because bogus-IP
     (False, True, False, '1337'),  # no DNS because bogus-IP
     (False, True, True, 'deadbeef'),
-    (False, True, False, '31c3'),  # no DNS because bogus-IP
+    pytest.mark.xfail(qtutils.version_check('5.6.1'),
+                      reason='Qt behaviour changed')(
+            False, True, False, '31c3'),  # no DNS because bogus-IP
     (False, True, False, 'foo::bar'),  # no DNS because of no host
     # Valid search term with autosearch
     (False, False, False, 'test foo'),