Security Groups are no longer inherited from the master instance

To better accomodate integration with Neutron and to move into
the direction of using core nova boot functionality to launch
instances, security groups will no longer be inherited from the
master instance. This implies that any non-default security group
will need to be specified at launch time.

Fixes OS-201

Change-Id: I594bdfe653eec570817cc7c61f75e3902acf371e