Launch Instance NG does not auto select default security group or default to selecting the only network in a Project

[Peter Nordquist]

In the Mitaka Release of Horizon, the Launch Instance NG panels do not select the 'default' security group and if there is only one network in a Project it does not default to that network. In the Launch Instance Legacy workflow, this defaulted to the 'default' security group and if you only had one network it defaulted to select that network. In Mitaka, the Launch Instance Legacy workflow no longer selects the 'default' security group since it is defaulting to using the string instead of the id of the 'default' network and this change broke that [0]. I'm not expecting the Launch Instance Legacy workflow to be fixed, just documenting that fact since I switched back to that workflow expecting it to work like the Kilo dashboard.

[0]: https://github.com/openstack/horizon/commit/5562694