non zero exit codes for classes scripts

[Thomas Lange]

Hi Martin,

I can find no change that causes a change in the behaviour for that
between 5.8.1 and the newest FAI version. As you pointed out an "exit X"
in a .sh script causes fai-class to stop defining more classes. You
can try to set an error code inside a .sh file by using a call to
task_error xxx. I'm not sure if this will work, since fai-class runs in a
subprocess.
After looking into the code it seems that fai-class almost always ends
with exit 0.

-- 
regards Thomas