use _exit for quitting the child process in test_wait.rs.

Author: marmistrz

test/sys/test_wait.rs

@@ -42,7 +42,7 @@ fn test_waitstatus_pid() {
     let _m = ::FORK_MTX.lock().expect("Mutex got poisoned by another test");
 
     match fork().unwrap() {
-        Child => {},
+        Child => unsafe { _exit(0) },
         Parent { child } => {
             let status = waitpid(child, None).unwrap();
             assert_eq!(status.pid(), Some(child));