Fix scenario base functions

There were two issues introduced in [1] which are fixed here:

- Calling create_server() with parameter security_groups=None fails,
  we need to use the "default" group instead of passing "None" to nova.
- The signature of create_secgroup_rules() was changed, we need to
  append the new parameter at the end in order to preserve
  compatibility with existing callers.

[1] I711a10eef321622c335e35b84e386b01d73b938a
Change-Id: I506dfa66378a9c7c59e2296f35f88613a1bd3af1
1 file changed