Attempt 1: make sure to always flush buffered logs

Previously, buffered logs would sometimes not get flushed resulting in
lost test report output. See scalameta#408. This commit adds an extra attempt to
flush the buffered logs inside the sbt testing framework in case the
logs don't get flushed by the JUnit test listener. I'm not 100% sure
this fixes the problem but it seems worth a short and it shouldn't cause
a regression.

junit-interface/src/main/java/munit/internal/junitinterface/EventDispatcher.java

@@ -159,7 +159,6 @@ public void testRunFinished(Result result)
           ", " +
           result.getIgnoreCount()+" ignored" +
           ", "+result.getRunCount()+" total, "+(result.getRunTime()/1000.0)+"s") ;
-        logger.flush();
       }
     runStatistics.addTime(result.getRunTime());
   }
@@ -174,7 +173,6 @@ public void testRunStarted(Description desc)
   {
       if (settings.verbose) {
         logger.info(taskInfo + " started");
-        logger.flush();
       }
   }
 
@@ -183,7 +181,6 @@ void testExecutionFailed(String testName, Throwable err)
     post(new Event(Ansi.c(testName, Ansi.ERRMSG), settings.buildErrorMessage(err), Status.Error, 0L, err) {
       void logTo(RichLogger logger) {
         logger.error(ansiName+" failed: "+ansiMsg, error);
-        logger.flush();
       }
     });
   }

junit-interface/src/main/java/munit/internal/junitinterface/JUnitTask.java

@@ -79,6 +79,7 @@ public Task[] execute(EventHandler eventHandler, Logger[] loggers) {
         ed.testExecutionFailed(testClassName, ex);
       }
     } finally {
+      logger.flush();
       settings.restoreSystemProperties(oldprops);
     }
     return new Task[0]; // junit tests do not nest