Change the py.test lines to specify a basetemp.
Change the py.test lines to specify a basetemp.

This is a file in /var/tmp, which is on the real filesystem.
This makes it more likely that we can generate very large
files for some of the bigger tests.

Signed-off-by: Chris Lalancette <281cd07d7578d97c83271fbbf2faddb83ab3791c@openrobotics.org>

clalancette/pycdlib,clalancette/pyiso