Tries to guess the url of zabbix frontend.

    .. versionadded:: 2016.3.0

def _frontend_url():
    '''
    Tries to guess the url of zabbix frontend.

    .. versionadded:: 2016.3.0
    '''
    hostname = socket.gethostname()
    frontend_url = 'http://' + hostname + '/zabbix/api_jsonrpc.php'
    try:
        try:
            response = salt.utils.http.query(frontend_url)
            error = response['error']
        except HTTPError as http_e:
            error = six.text_type(http_e)
        if error.find('412: Precondition Failed'):
            return frontend_url
        else:
            raise KeyError
    except (ValueError, KeyError):
        return False