Tiny rework on JS file

Hello, interesting module and idea! Really great work you did here.

I had an issue where if you have "Bootstrap Modal Login" module activated and you are navigating to /user , due to the fact that there are 3 separate login forms active at the same time (1 in /user/login + 2 in modal form as hidden), some things were rendering multiple times. Eg. the "Clear" button and the entered codes from the keypad (after the 1st failure, not from the beginning).

So I had to rework a little bit the JS file because it was triggering multiple times after a failed attempt and was rendering the "Clear" button 3 times as well.

In reality, I moved the "Clear" button inside the form's code instead of JS plus some minor cleanup (really minor).