Fix failure, add tests.

* bzrlib/tests/test_selftest.py:
(TestTestResult.test_startTests.InstrumentedTestResult): Check
that startTests is called once.
(TestRunSuite.test_runner_class): Check that
ExtendedTestResult.done() is called once.

* bzrlib/tests/blackbox/test_selftest.py:
(TestBenchmarkTests.test_benchmark_runs_benchmark_tests): Output
order has changed.

* bzrlib/tests/__init__.py:
(run_suite): At least subunit.TestProtocolClient doesn't define
done().