message: [consensus] cleanup safety rules thread
  Eliminate the dead code warning. We don't really need to keep this
  handle, but I think it is worthwhile to keep around so that once we
  implement tear down we can test it appropriately in this domain.
  Closes:
  Approved by: davidiw
diff: // Copyright (c) The Libra Core Contributors
  // SPDX-License-Identifier: Apache-2.0
  -#![allow(dead_code)]
  -
  //! This provides a execution separation between SafetyRules and Consensus without requiring the
  //! use of processes. Rust does not support fork and so the mechanics to actually construct a
  //! SafetyRules that would run together and be started by Consensus requires a separate binary and
  @@ -25,7 +23,7 @@ use std::{
  /// ThreadClient is the actual owner of the thread but in the context of Consenus and SafetyRules
  /// is on the client side of the operations as it makes queries / requests to SafetyRules.
  pub struct ThreadService<T> {
  - child: JoinHandle<()>,
  + _child: JoinHandle<()>,
  server_addr: SocketAddr,
  marker: PhantomData<T>,
  }
  @@ -41,7 +39,7 @@ impl<T: Payload> ThreadService<T> {
  });
  Self {
  - child,
  + _child: child,
  server_addr,
  marker: PhantomData,
  }
  