Create default net in ImagesNegativeTestJSON

As the test result [1] showed we missed ImagesNegativeTestJSON when
fixed https://bugs.launchpad.net/tempest/+bug/1844568

Related-Bug: #1844568

[1] https://storage.gra.cloud.ovh.net/v1/AUTH_dcaab5e32b234d56b626f72581e3644c/zuul_opendev_logs_7a3/846187/3/check/nova-next/7a30291/testr_results.html

Change-Id: Ibd12542ee08f5020eddafcb253a978ac50f9e53a
diff --git a/tempest/api/compute/images/test_images_negative.py b/tempest/api/compute/images/test_images_negative.py
index 5ff2a6a..124651e 100644
--- a/tempest/api/compute/images/test_images_negative.py
+++ b/tempest/api/compute/images/test_images_negative.py
@@ -43,6 +43,7 @@
 
 class ImagesNegativeTestJSON(ImagesNegativeTestBase):
     """Negative tests of server image"""
+    create_default_network = True
 
     @decorators.attr(type=['negative'])
     @decorators.idempotent_id('6cd5a89d-5b47-46a7-93bc-3916f0d84973')