List all available configs

    CLI example:

    .. code-block:: bash

        salt '*' snapper.list_configs

def list_configs():
    '''
    List all available configs

    CLI example:

    .. code-block:: bash

        salt '*' snapper.list_configs
    '''
    try:
        configs = snapper.ListConfigs()
        return dict((config[0], config[2]) for config in configs)
    except dbus.DBusException as exc:
        raise CommandExecutionError(
            'Error encountered while listing configurations: {0}'
            .format(_dbus_exception_to_reason(exc, locals()))
        )