Encrypt Compute metadata traffic

OpenStack Juno supports encrypting Compute metadata traffic with HTTPS. Enable SSL encryption in the metadata_agent.ini file:

Enable the HTTPS protocol:
```
nova_metadata_protocol = https
```
Determine whether insecure SSL connections are accepted for Compute metadata server requests. The default value is False:
```
nova_metadata_insecure = False
```
Specify the path to the client certificate:
```
nova_client_cert = PATH_TO_CERT
```
Specify the path to the private key:
```
nova_client_priv_key = PATH_TO_KEY
```