Bug#766902: @reboot jobs are run on package installation

[Alexandre Detiste]

> It is fixed in two places:

.. but newly added @reboot jobs will still be executed right away.

http://www.freedesktop.org/software/systemd/man/systemd.timer.html
> If a timer configured with OnBootSec= or OnStartupSec= is already in the past
> when the timer unit is activated, it will immediately elapse and the configured unit is started.

Simply creating /run/crond.reboot at the end of the generator 
conflicts with a work around for another non-solved bug:

TL;DR: when /var is mounted separately, the generator needs to be run twice.

https://github.com/systemd-cron/systemd-cron/issues/26
http://lists.freedesktop.org/archives/systemd-devel/2014-October/024239.html

--

crontab will now create /run/crond.reboot too,
in order to mitigate this bug

https://github.com/systemd-cron/systemd-cron/commit/5da457fbd837dd6371a9858a2a4abfa8c9b495ac