Issue tracker "+1" confirmation dialogue should abort when the user clicks outside the dialogue window (BB-16094)

The issue tracker warns users when they try to submit a comment containing only the string "+1" and offers them the choice to either submit the comment as-is or to discard the comment and submit a vote for the issue instead.

Current behaviour: When the user clicks the greyed out background outside the dialogue window, the comment is submitted as-is.

Expected behaviour: When the user clicks the greyed out background outside the dialogue window, the action is aborted and focus is returned to the comment text input.