fix: exit with error on retry give up

When browser not responding karma just logs `ERROR [launcher]: <browser> failed 2 times (timeout). Giving up.` and hangs.

We should exit with error in such case.
Good question... Seems like because nobody calls `self._done`. In our case `karma-webdriver-launcher` just calls `self.emit('done')` and skips this code. Looks like we need to fix `karma-webdriver-launcher`.