gluon-web-model: update inputs on form reset

Register to 'reset' event on form element and make call to 'update' function
delayed in 'data-update' handler to allow the form values to update beforehand.

When using a form's 'reset' button, form field visibility was not updated.
This could lead to situations where a checkbox had to be toggled again
twice to display the detail text inputs. (Example taken from private
wifi package)

(cherry picked from commit bf090a8a)