pkg/fileutil: fix shadowed variables

pkg/fileutil/fileutil_test.go

@@ -52,7 +52,7 @@ func TestReadDir(t *testing.T) {
 		if err != nil {
 			t.Fatalf("error creating file: %v", err)
 		}
-		if err := fh.Close(); err != nil {
+		if err = fh.Close(); err != nil {
 			t.Fatalf("error closing file: %v", err)
 		}
 	}

pkg/fileutil/lock_test.go

@@ -28,7 +28,7 @@ func TestLockAndUnlock(t *testing.T) {
 	}
 	f.Close()
 	defer func() {
-		err := os.Remove(f.Name())
+		err = os.Remove(f.Name())
 		if err != nil {
 			t.Fatal(err)
 		}

pkg/fileutil/purge_test.go

@@ -121,7 +121,7 @@ func TestPurgeFileHoldingLock(t *testing.T) {
 	}
 
 	select {
-	case err := <-errch:
+	case err = <-errch:
 		t.Errorf("unexpected purge error %v", err)
 	case <-time.After(time.Millisecond):
 	}