protected Properties getNonBlockingRouterProperties(String routerDataCenter) {
    return getNonBlockingRouterProperties(routerDataCenter, PUT_REQUEST_PARALLELISM, DELETE_REQUEST_PARALLELISM);
  }
Constructs and returns a VerifiableProperties instance with the defaults required for instantiating
the {@link NonBlockingRouter}.
@return the created VerifiableProperties instance.
ambry-router/src/test/java/com/github/ambry/router/NonBlockingRouterTestBase.java