veyron/lib/modules: Clean up stderr files on Shutdown

Change-Id: I35cedaacec3dfd211b5a36fa9333a76abd243796
diff --git a/lib/modules/util.go b/lib/modules/util.go
index b38e767..b2a62fa 100644
--- a/lib/modules/util.go
+++ b/lib/modules/util.go
@@ -16,7 +16,7 @@
 
 func newLogfile(prefix, name string) (*os.File, error) {
 	nameHash := adler32.Checksum([]byte(name))
-	f, err := ioutil.TempFile("", fmt.Sprintf("__modules__%s-%x", prefix, nameHash))
+	f, err := ioutil.TempFile("", fmt.Sprintf("__modules__%s-%x-", prefix, nameHash))
 	if err != nil {
 		return nil, err
 	}