void awaitBlobReplicates(String blobId) {
    try {
      waitForTracker(blobId);
      EventTracker et = objectTracker.get(blobId);
      if (!et.awaitBlobReplicates()) {
        Assert.fail("Failed awaiting for " + blobId + " on-demand-replication");
      }
    } catch (InterruptedException e) {
      // ignore
    }
  }
Waits for blob on-demand-replication happens on one single replica for {@code blobId}
For ODR, we usually only replicate to one single replica
@param blobId the ID of the blob
ambry-test-utils/src/main/java/com/github/ambry/server/MockNotificationSystem.java