Tidy up use declaration syntax.

lib/filetests/src/concurrent.rs

@@ -7,13 +7,14 @@ use cranelift_codegen::dbg::LOG_FILENAME_PREFIX;
 use cranelift_codegen::timing;
 use file_per_thread_logger;
 use num_cpus;
+use runone;
 use std::panic::catch_unwind;
 use std::path::{Path, PathBuf};
 use std::sync::mpsc::{channel, Receiver, Sender};
 use std::sync::{Arc, Mutex};
 use std::thread;
 use std::time::Duration;
-use {runone, TestResult};
+use TestResult;
 
 /// Request sent to worker threads contains jobid and path.
 struct Request(usize, PathBuf);