test: cleanup neutron security group

I kept running into partial-cleanups and other issues with the `create.yml` code and felt this would be a good chance to help re-stage the test environment when setting up and tearing it down.
I liked getting the actual output when I would hit the '409' issue but didn't care when the rule didn't exist to be deleted.
Probably a better way to define the failing criteria than straight-up ignoring it like this. :)