private void startAwaitCreation(final OperationChain opChain) {
    notificationSystem.awaitBlobCreations(opChain.blobId);
    continueChain(opChain);
  }
Using the mock notification system, wait for the put blob in this operation chain to be replicated to all server
nodes before continuing the chain.
@param opChain the {@link OperationChain} object that this operation is a part of.
ambry-server/src/integration-test/java/com/github/ambry/server/RouterServerTestFramework.java