Fix toolbox failure return to match similar tools.

Bug: https://code.google.com/p/android/issues/detail?id=182226
Change-Id: Ib05709b8f9b474d5989b69abd949a6dc661af998
diff --git a/toolbox/toolbox.c b/toolbox/toolbox.c
index 6bce5ed..b5a942c 100644
--- a/toolbox/toolbox.c
+++ b/toolbox/toolbox.c
@@ -42,7 +42,7 @@
     }
 
     printf("%s: no such tool\n", argv[0]);
-    return -1;
+    return 127;
 }
 
 int toolbox_main(int argc, char** argv) {