Return public_vip and management_vip in network_configuration handler.

unit-tests

* remove ostf specific handlers
* add public_vip and management_vip in network_configuration handler

```
GET /api/clusters/7/network_configuration
{
    "public_vip": "240.0.1.2" # if mode is HA
    "management_vip": "192.168.0.2",  # if mode is HA
}
```