Description:
------------
failure_callback does not work for session handler. Parameter is not recognized in 
PS_OPEN_FUNC.

Test script:
---------------
$session_save_path = "tcp://$unreachableHost:$unreachablePort?failure_callback=_callback_server_failure";
ini_set('session.save_handler', 'memcache');
ini_set('session.save_path', $session_save_path);

function _callback_server_failure($host, $tcp_port, $udp_port, $error, $errnum) {
  echo "true";
}

session_start();



Expected result:
----------------
true

Actual result:
--------------
Warning: Unknown: Failed to write session data (memcache). Please verify that the 
current setting of session.save_path is correct (tcp://10.254.254.254:11211?
failure_callback=_callback_server_failure) in Unknown on line 0