Inconsistently set validator.settings['name_event'] leads to trouble with ajax validators [#2835954]

Problem/Motivation

Ajax handlers use following code to avoid to may requests to the backend:

      // Do not fire on every keystroke. Ajax callbacks are expensive.
      if (this.settings['name_event'] == 'onkeyup') {
        return true;
      }

To be able to do this jquery.validate.js was adjusted to set that variable in function delegate(event) {.
Unfortunately it seems that there are cases in which delegate() isn't triggered and the call goes directly through:

// validate the form on submit
this.submit( function( event ) {

in jquery.validate.js.
If that happens validator.settings['name_event'] won't reflect the submit event but the last one that was handled by delegate().

This can lead to situations in which a submit is processed without triggering the validation at all.