oeqa/concurrencytest: Avoid unclosed file warnings

Avoid an unclosed file per thread warning when running selftests concurrently
by closing the result stream.

(From OE-Core rev: 33a4a076e8aa72a872807332501e7f5ae1cee0e2)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/core/utils/concurrencytest.py

@@ -115,6 +115,9 @@ class ConcurrentTestSuite(unittest.TestSuite):
             for thread, process_result in threads.values():
                 process_result.stop()
             raise
+        finally:
+            for test in tests:
+                test[0]._stream.close()
 
     def _run_test(self, test, process_result, queue):
         try: