Bug#619376: kdm: does not start with parallel boot

[f.rougon@free.fr]

One possible reason if this problem happens intermittently is the
following: you may have a program such as ntpdate or rdate that starts
in parallel with other init scripts such as KDM e.g., when some network
interface is brought up, and steps the system clock by such an amount
that the KDM timeout for X server startup (30 s by default) is exceeded.

In the case of ntpdate, one possible fix is to disable
/etc/network/if-up.d/ntpdate and run ntpdate in the *foreground* from
/etc/init.d/networking in the "start)" case after successful "ifup -a"
call and the corresponding LSB logging message. Unfortunately, by
default rsyslog is started later, in normal runlevels, therefore one
cannot use the -s ntpdate option in this setup. Another little problem
with this solution is that the clock may be stepped every time you do:

  invoke-rc.d networking start

whereas it would be desirable to limit clock stepping to the (early)
boot process. One might use a "flag" file for that, but I hope there are
more elegant ways...