Fixed wrong path to pngoverlay-cairo

Caramel reported the problem:

https://forum.puppylinux.com/viewtopic.php?p=163558#p163558

The problem is that pngoverlay-cairo is in /usr/sbin, not in /usr/bin

In Easy Scarthgap, /usr/sbin is a symlink to /usr/bin, so the problem never occurred.

This affected two scripts, /usr/local/sfsget/dir2sfs and /usr/local/easy_containers/easy-containers, now fixed.    

Tags: easy