Set an environment variable for the Sidekiq logfile path.
Set an environment variable for the Sidekiq logfile path.

This will be needed as of alphagov/publisher#1603. See that PR for
context.

https://trello.com/c/Jef1t4xU

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet