(SERVER-2780) Use puppetdb 7 nightly builds
(SERVER-2780) Use puppetdb 7 nightly builds

This commit updates the puppetdb stream we test with to Platform 7,
which has the API updates needed to take up this HTTP client update.

puppetlabs/puppetserver,puppetlabs/puppetserver,puppetlabs/puppetserver,puppetlabs/puppet-server,puppetlabs/puppet-server,puppetlabs/puppetserver,puppetlabs/puppet-server