Condition check before ending the main thread.

Make sure the main thread waits for the child thread with the Run() method.

* Add this at the end of your Run() method for each device:
```
boost::lock_guard<boost::mutex> lock(fRunningMutex);
fRunningFinished = true;
fRunningCondition.notify_one();
```
* Then you must replace the `char ch; cin.get(ch);` in your main() function with:
```
boost::unique_lock<boost::mutex> lock(processor.fRunningMutex);
while (!processor.fRunningFinished)
{
    processor.fRunningCondition.wait(lock);
}
```

fairmq/devices/FairMQBenchmarkSampler.cxx

@@ -76,6 +76,11 @@ void FairMQBenchmarkSampler::Run()
     }
 
     FairMQDevice::Shutdown();
+
+    // notify parent thread about end of processing.
+    boost::lock_guard<boost::mutex> lock(fRunningMutex);
+    fRunningFinished = true;
+    fRunningCondition.notify_one();
 }
 
 void FairMQBenchmarkSampler::ResetEventCounter()