Revert "Monitor age of daily.cvd rather than daily.cld"
Revert "Monitor age of daily.cvd rather than daily.cld"

This reverts commit f1b6b7b7de057842556403be837938b141b003bb.

This is causing false positives in Preview since it was deployed - it
seems that the `daily.cvd` file is not always present.

See also 0037581a3.

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