Don't re-extract mongo dumps.
Don't re-extract mongo dumps.

This matches what the Mysql and Postgresql scripts do, and creates a
flag file after extracting.  This means we don't then re-extract a
tarball that's already been extracted.

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