Only preventDefault on click on [data-toggle="modal"] when the element is a link

In it's current state Bootstrap always prevents the default action for a click
event on `[data-toggle="modal"]` elements
(see https://github.com/twbs/bootstrap/blob/master/js/modal.js#L233).
Instead this should only happen when the element is a link.
Merge pull request #10834 from Prinzhorn/master

Only preventDefault on click on [data-toggle="modal"] when the element is a link