Fix tag-prefix to not abort on $timeout.

Fix tag-prefix to not abort on $timeout.

If $timeout is set very low, then it can cancel the tag-prefix before
the user has time to press the desired command.

Change the code to set the tag flag, and then recontinue with normal
event processing instead.  Cancel on an abort, but continue with a timeout.

Thanks to Lauri Tirkkonen for reporting the issue.