Simplify the walk_directories logic.
Simplify the walk_directories logic.

Now that we look at things by extent, we can actually get
rid of a workaround.

Signed-off-by: Chris Lalancette <281cd07d7578d97c83271fbbf2faddb83ab3791c@gmail.com>

clalancette/pycdlib,clalancette/pyiso