Security groups: prevent race for default security group creation

When a VM is booted via the Nova the client connection is created
with an admin user. This causes problems when creating the neutron
port. That is, there may be a race for the creation of the default
security group for the tenant.
The problem was introduced by commit acf44dba26ca8dca47bfb5fb2916807f9f4e2060

Change-Id: Ie0199c71231a322704f1f49995facde09c92da25
Closes-bug: #1372570
Merge "Security groups: prevent race for default security group creation"