poudriere ignores stored options after r429298

[Stefan Ehmann]

After today's ports update, poudriere ignores all options that were 
previously stored.

Everything works as before after reverting r429298 "Make the ports 
infrastructure accept at least 3 level ports"

Previously, poudriere stored its options for python27 in
/usr/local/etc/poudriere.d/options/lang_python27

Now options are stored in
/usr/local/etc/poudriere.d/options/_usr_ports_lang_python27