UCLOUDNG 534: Revised pre-defined network implementation

1. Revised config name to 'pre_defined_network'
2. Revised to get pre_defined_network ID at nova-compute initialize step. If it fails, nova-compute fails to start with "ERROR nova.network [-] Pre-defined network required, but not specified" if the config is missing or "QuantumClientException: Unable to find network with name 'multihost-net-02'" if the name of the network is not available.
3. Revised disabling non-pre-defined network codes