bootserver: add cups watchdog script

Sometimes, in some environments, cups (at least 1.5.3-0ubuntu8) seems to
jam and stop processing printing jobs. The jam can be detected by
running lpstat and checking if it blocks.

This script acts as a watchdog, restarting cups if it seems to be jammed
(=lpstat blocks for over 4 seconds).

And yes, I know it's quite sad that we have to make this kind of hack,
but finding the real bug and fixing it properly is at least 42 times
harder and slower than writing and delivering this script.

And this script just seems work, without any known significant
drawbacks.
bootserver: add upstart script for cups-watchdog
ci.sh: upload only if --upload is passed as the first arg