Fix normalize parameters

Hmm... what if I really want to have "isUndefined" method on server? %)
```js
var method = new ApiMethod({
    name : 'isUndefined',
    params : { value : { required : true }},
    action : function(params) { return params.value === undefined; }
});
method.exec({ value : undefined }); // missing value parameter =(
```