New handling of LOGDIR

[Thomas Lange]

This is a short proposal or documentation how to handle the usage
and setting of LOGDIR.

Goals
-------
- remove usage of /var/log/fai/current during softupdate
- do not call rm -rf $LOGDIR
- Always log to /var/log/fai/$HOSTNAME/$FAI_ACTION-date_time (using $fai_rundate)



We distinguish between the initial installation (from network or CD),
and calling fai with action softupdates or dirinstall.

When doing softupdate or dirinstall fai can directly use
LOGDIR=/var/log/fai/$HOSTNAME/$FAI_ACTION-date_time, since we have all
data (action, date, time, hostname) for setting it in the very
beginning. In this case, there's no need at all to remove LOGDIR
before.

When doing an initial installation (do_init_task=1), information like
FAI_ACTION, time and hostname aren't available in the early beginning
(or may change when calling scripts in class/). So in this case it's
fine to use LOGDIR=/var/log/fai/current during the installation (there
will be no other fai process running at the same time) and to copy
this subdirectory to /var/log/fai/$HOSTNAME/$FAI_ACTION-date_time at
the end of the installation (as currently done in FAI).

Any comment? I will start to implement this right now (after lunch :-).

-- 
regards Thomas