Return available OpenNebula locations.

    CLI Example:

    .. code-block:: bash

        salt-cloud --list-locations opennebula
        salt-cloud --function avail_locations opennebula
        salt-cloud -f avail_locations opennebula

def avail_locations(call=None):
    '''
    Return available OpenNebula locations.

    CLI Example:

    .. code-block:: bash

        salt-cloud --list-locations opennebula
        salt-cloud --function avail_locations opennebula
        salt-cloud -f avail_locations opennebula

    '''
    if call == 'action':
        raise SaltCloudSystemExit(
            'The avail_locations function must be called with '
            '-f or --function, or with the --list-locations option.'
        )

    server, user, password = _get_xml_rpc()
    auth = ':'.join([user, password])
    host_pool = server.one.hostpool.info(auth)[1]

    locations = {}
    for host in _get_xml(host_pool):
        locations[host.find('NAME').text] = _xml_to_dict(host)

    return locations