minor comments update

repo/common/proxy.rc.local

@@ -1,3 +1,7 @@
+#!/bin/bash
+
+# Automatic proxy configuration on startup for sandboxed machines
+
 apt_proxy=/etc/apt/apt.conf.d/00proxy
 proxy_line=$(cat $apt_proxy | awk '{print $2}')
 proxy_srv=$(echo $proxy_line | cut -d'/' -f 3 | cut -d':' -f 1)