Update all the apt caches updates with a timeout

One of the longest processes in an ursula run is the cache update. So,
dont do it if we dont really need to.
apt_repository does not accept cache_valid_time

So remove it from all of those resources.
Fix more stray cache_valid_time attributes

I left a few out from the previous commit.
Merge pull request #428 from craigtracey/cachetime

Update all the apt caches updates with a timeout