Clean shutdown for subcommands (#6909)

substrate/client/cli/src/runner.rs

@@ -96,7 +96,7 @@ pub fn build_runtime() -> std::result::Result<tokio::runtime::Runtime, std::io::
 fn run_until_exit<FUT, ERR>(
 	mut tokio_runtime: tokio::runtime::Runtime,
 	future: FUT,
-	mut task_manager: TaskManager,
+	task_manager: TaskManager,
 ) -> Result<()>
 where
 	FUT: Future<Output = std::result::Result<(), ERR>> + future::Future,
@@ -106,9 +106,7 @@ where
 	pin_mut!(f);
 
 	tokio_runtime.block_on(main(f)).map_err(|e| e.to_string())?;
-
-	task_manager.terminate();
-	drop(tokio_runtime);
+	tokio_runtime.block_on(task_manager.clean_shutdown());
 
 	Ok(())
 }