Horizontal scrollbar in IE11 for Add To Group modal

Follow up of https://github.com/topcoder-platform/u-bahn-app/issues/155

From the changes in that ticket, we are now seeing a horizontal scrollbar in the Add To Group modal - in IE11 browser.

Expected - we should NOT see the horizontal scrollbar in the Add To Group modal. Virtual scrolling should continue to work as before as so should all other features.

Final Submission Guidelines

Git issue link: https://github.com/topcoder-platform/u-bahn-app/issues/621