Create default net in ImagesNegativeTestJSON
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

openstack/tempest,openstack/tempest