Set max heap size for puppetserver to 8G
Set max heap size for puppetserver to 8G

- We encounter OOM kills of the puppetserver

- There is no direct comparison to the ruby version in staging, but
  between threads that instance seem to use 6G+ RAM

- Changing the default of 2G manually to 8G has increased stability

@schmie

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