Heat wants to use 'novaclient.v2.servers.
ServerManager._console' method to simplify the
implementation of retrieving server console.
It's better to change the method to public for
public use.
The patch changes:
1. add public method named get_console_url() for class
'novaclient.v2.servers.Server'
2. rename _console() to get_console_url() for class
'novaclient.v2.servers.ServerManager'
Change-Id: I3d1485468d1d0a79d4002981ebe05b6cdf2332e7
Closes-Bug: #1651677