cosmetic: flush stdout and stderr before printing summary

Change-Id: I9c7eec29c200ec90e9908457a07b79122014a0e9
diff --git a/src/osmo-gsm-tester.py b/src/osmo-gsm-tester.py
index 725b0a3..b834711 100755
--- a/src/osmo-gsm-tester.py
+++ b/src/osmo-gsm-tester.py
@@ -168,6 +168,8 @@
                 current_trial.err('FAIL')
                 trials_failed.append(current_trial.name())
 
+    sys.stderr.flush()
+    sys.stdout.flush()
     if trials_passed:
         print('Trials passed:\n  ' + ('\n  '.join(trials_passed)))
     if trials_failed: