Tidy up remove lumberjack

This just removed what we added in in the recent switch to
logstashforwarder. It seems there are a few other resources related to
lumberjack still lying around.
Fix check - fire if no new logs for 5 data points

As it stands logs are too bursty and the check frequency is too fine -
we are getting intermittent alerts due to no logs for a very short
period of time.
Merge pull request #688 from alphagov/tidy-up-remove-lumberjack

Tidy up remove lumberjack
Merge pull request #689 from alphagov/fix-logging-rate-check

Fix check - fire if no new logs for 5 data points