Code review comment for lp:~wallyworld/juju-core/instance-default-secgroup

I added a comment to bug 1129720 about the general approach.

I agree with William that adding more config here isn't really
desirable, but just putting the default group on all machines juju
creates is a step back in our general isolation level. The
per-environment security group is a much cleaner place to add custom
rules, even if we don't supply a juju command for doing that (though we
could).

Code itself looks fine.

https://codereview.appspot.com/44770044/