`karma start --single-run` does not exit cleanly with WinXP/IE8

When I try to execute a `--single-run` of Karma with `browsers: ['IE']`, on WinXP/IE8, Karma does not exit cleanly but rather hangs at the prompt waiting for me to terminate the process. Other browsers do not exhibit this behavior on XP.

Start by reproducing `karma start --single-run` with `browsers: ['IE']` on WinXP/IE8 and compare its shutdown behavior with other browsers on XP. Trace the `karma start` single-run entry point and identify why the process remains at the prompt; done means the run exits cleanly without manual termination.

Written by the indexing model from the issue text.