Fix Focus war with modals

Bootstrap's modal (and maybe others) require focus to maintain in the modal (because that what a modal is). The dropdown is outside of the modal, so we need to stopPropagation on the focusin event so the modal doesn't try to steal back the focus.

This bug was causing an infinte loop of focus being set between the modal and select2. It is tough on the browser and prevents the search input from working at all.