'Get a list of security groups.
The listing result is an object with property "items". Each item is
a security group.
Example GET:
http://localhost/api/network/securitygroups'

@rest_utils.ajax()
def get(self, request):

    security_groups = api.neutron.security_group_list(request)
    return {'items': [sg.to_dict() for sg in security_groups]}
