[Stateless SG] Fix usage of the default stateless SG

In the test test_default_sec_grp_scenarios default SG from project is
used. In the stateless tests suite this group wasn't really stateless
as default group is always created as stateful initiall.
This patch adds update of the SG to ensure that it is stateless when
needed.

Change-Id: I6774f586b1a0a531d277cf5954737a0dfd1f2a5c
1 file changed