Simplify code

Author: newpavlov

src/use_file.rs

@@ -63,26 +63,24 @@ fn get_rng_fd() -> Result<libc::c_int, Error> {
                 }
                 val => return Ok(val as libc::c_int),
             }
-            let res = FD.compare_exchange_weak(
+
+            let xch_res = FD.compare_exchange_weak(
                 FD_UNINIT,
                 FD_ONGOING_INIT,
                 Ordering::AcqRel,
                 Ordering::Relaxed,
             );
-            if res.is_err() {
+            if xch_res.is_err() {
                 continue;
             }
 
-            return match open_fd() {
-                Ok(fd) => {
-                    FD.store(fd as usize, Ordering::Release);
-                    Ok(fd)
-                }
-                Err(err) => {
-                    FD.store(FD_UNINIT, Ordering::Release);
-                    Err(err)
-                }
+            let res = open_fd();
+            let val = match res {
+                Ok(fd) => fd as usize,
+                Err(_) => FD_UNINIT,
             };
+            FD.store(val, Ordering::Release);
+            return res;
         }
     }