Unskip multiselect exception test

[Robdel12]

It seems something in ember 2.11.3 broke testing any code that throws exceptions. We have a test that ensures a multiselect value is an array, and if its not throw. This test will break all the tests since that throw actually happens in the test suite now.

Check this ticket to possibly see progress: emberjs/ember.js#15013

(Introduced in #183)