The problem is that you don't have a result named "SUCCESS", just like the error message says: the default result name is "success". Instead of just using the Struts 2 Action.SUCCESS value (which is "success") you're using a user-defined value that isn't reflected in your configuration file.
Dude simply change the result page location.
create a folder with name content in web-inf directory and place all your result pages in that location and run the server that must do
in struts 2 it looks for a folder with name content in web inf.
Hope this helps