title: Avoiding duplicating PeriodicWorkRequest from WorkManager
body: <p>On Application start I want to start service that will work forever, but when user opens app again it duplicates.</p>
  
  <pre><code>PeriodicWorkRequest.Builder sendDataBuilder = new PeriodicWorkRequest.Builder(SendConnectionMetricsWorker.class, Constants.REPEAT_TIME_INTERVAL_IN_HOURS, Constants.REPEAT_TIME_INTERVAL_UNITS)
                  .setConstraints(new Constraints.Builder()
                          .setRequiredNetworkType(NetworkType.CONNECTED)
                          .build());
          PeriodicWorkRequest periodicWorkRequest = sendDataBuilder
                  .build();
          WorkManager.getInstance().enqueue(periodicWorkRequest);
  </code></pre>