tests: cleanup properly in wait_on_fail decorator

Close transport used to wait for user input, otherwise all further tests
would fail on cleanup (FD leak detected). This in practice is only
useful when using wait_on_fail decorator without --failfast option.

(cherry picked from commit e382655)

qubes/tests/__init__.py

@@ -251,6 +251,7 @@ def wrapper(self, *args, **kwargs):
                     lambda: asyncio.StreamReaderProtocol(reader),
                     sys.stdin))
             self.loop.run_until_complete(reader.readline())
+            transport.close()
             raise
 
     return wrapper