bpo-44955: Always call stopTestRun() for implicitly created TestResult objects (GH...

bpo-44955: Always call stopTestRun() for implicitly created TestResult objects (GH-27831)

Method stopTestRun() is now always called in pair with method startTestRun()
for TestResult objects implicitly created in TestCase.run().
Previously it was not called for test methods and classes decorated with
a skipping decorator.