message: test: Fix server RequestDeviceList so tests will pass
  The server is still basically a stub implementation for now, but needs
  a proper response to RequestDeviceList otherwise tests will fail.
diff: pub mod device_manager;
  use crate::core::errors::*;
  -use crate::core::messages;
  -use crate::core::messages::ButtplugMessage;
  -use crate::core::messages::ButtplugMessageUnion;
  +use crate::core::messages::{self, ButtplugMessage, ButtplugMessageUnion};
  use async_std::sync::Sender;
  /// Represents a ButtplugServer.
  @@ -55,6 +53,11 @@ impl ButtplugServer {
  || Result::Ok(ButtplugMessageUnion::Ok(messages::Ok::new(msg.get_id()))),
  Result::Err,
  ),
  + ButtplugMessageUnion::RequestDeviceList(_) => {
  + let mut list = messages::DeviceList::default();
  + list.set_id(msg.get_id());
  + Result::Ok(list.as_union())
  + }
  _ => Result::Ok(ButtplugMessageUnion::Ok(messages::Ok::new(msg.get_id()))),
  }
  }
  