get_launch_config should return all server values the API provides

Recently I submitted #445 to add `config_drive` and `user_data` parameters for creating and updating autoscale launch configs.

Unfortunately I did not realize it, but `get_launch_config` was hard coded to specify what data it would return.

This pull request updates `get_launch_config` to return all server values that the API provides.

This should be backwards and forwards compatible with any additional data that can be specified in the launch config.