nrwt: clean up exception handling and make sure we log some more failures

nrwt: clean up exception handling and make sure we log some more failures
https://bugs.webkit.org/show_bug.cgi?id=90503

Reviewed by Ojan Vafai.

There were several places where exceptions weren't getting
logged, most notably if you passed a bad value to --platform.
This change tests that and cleans things up a bit; more cleanup
will be possible when we rework the manager_worker_broker code.

* Scripts/webkitpy/layout_tests/controllers/manager_worker_broker.py:
(_BrokerConnection.raise_exception):
(_InlineWorkerConnection.raise_exception):
* Scripts/webkitpy/layout_tests/controllers/worker.py:
(Worker.run):
(Worker.kill_driver):
* Scripts/webkitpy/layout_tests/port/factory.py:
(PortFactory.get):
* Scripts/webkitpy/layout_tests/run_webkit_tests.py:
(run):
(main):
* Scripts/webkitpy/layout_tests/run_webkit_tests_integrationtest.py:
(MainTest.test_unsupported_platfrom):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121816 268f45cc-cd09-0410-ab3c-d52691b4dbfc