Add env var for bigquery credentials
Add env var for bigquery credentials

search-api doesn't use this var, but it will allow us to run the rake
task which needs these credentials without having to manually copy
credentials to the machine.

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