Invoke python version 2 explicitly for tools

Because it doesn't work with python3.

tools/pamusb-agent

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 #
 # Copyright (c) 2003-2007 Andrea Luzzardi <scox@sig11.org>
 #

tools/pamusb-conf

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 #
 # Copyright (c) 2003-2007 Andrea Luzzardi <scox@sig11.org>
 #