[#69107720] Don't rotate cdn logs in daily run.

Rename `/etc/logrotate.d/cdn_logs` to `/etc/logrotate.cdn_logs.conf` so that
it can be run independently of the main logrotate run triggered by
`cron.daily`.
[#69107720] Reconfigure cdn log rotation.

Configure log rotation of thecdn logs so that they can rotated more than
once a day.

* `rotate 8760`: keep a years worth if rotated hourly.
* `dateformat -%Y%m%d-%s`: make the date extension include unix epoch
  time so it is unique when rotated more than once a day.
* `size 1`: rotate if the file is larger than 1 byte. This basically
  forces a rotation on each run and negates the need for `daily` and
  `notifempty`
* remove `delaycompress`: With the addition of the `sleep 10` in the
  `postrotate` script there is no need to wait to compress since this
  happens after `postrotate` and `rsyslog` should have given up the file
  handles in that time.
[#69107720] Rotate cdn logs every hour.

Use cron.hourly to rotate the cdn logs every hour.
[#69107720] Process fastly logs every hour.

cron.hourly runs at 17 minutes past the hour. 13 minutes should be long enough
for the compression to finish.

The absent for the hour is required due to the unique way that
the `cron` type works http://docs.puppetlabs.com/references/latest/type.html#cron
Merge pull request #158 from alphagov/69107720_rotate_cdn_logs_hourly

rotate cdn logs hourly