address clippy lints

For intrepid commit message readers:
The choice to add allows for the inlined format args lint instead of actually
inlining them is not very clear because our actual real world MSRV is not clear.
We currently claim 1.60 is our MSRV but this is mainly due to dependencies. I'm
fairly sure that we could support < 1.58 if those deps are outdated in a users
lockfile. We'll remove these allows again at some point soon.

actix-http-test/src/lib.rs

@@ -2,6 +2,7 @@
 
 #![deny(rust_2018_idioms, nonstandard_style)]
 #![warn(future_incompatible)]
+#![allow(clippy::uninlined_format_args)]
 #![doc(html_logo_url = "https://actix.rs/img/logo.png")]
 #![doc(html_favicon_url = "https://actix.rs/favicon.ico")]
 
@@ -87,6 +88,7 @@ pub async fn test_server_with_addr<F: ServerServiceFactory<TcpStream>>(
 
         // notify TestServer that server and system have shut down
         // all thread managed resources should be dropped at this point
+        #[allow(clippy::let_underscore_future)]
         let _ = thread_stop_tx.send(());
     });
 
@@ -294,6 +296,7 @@ impl Drop for TestServer {
         // without needing to await anything
 
         // signal server to stop
+        #[allow(clippy::let_underscore_future)]
         let _ = self.server.stop(true);
 
         // signal system to stop