(maint) Refactor Docker test CLI invocations
(maint) Refactor Docker test CLI invocations

 - Move from using %x to popen2e

   %x seems to be causing problems with Azure runs, causing failures
   with no discernible output.

   For commands with no captured output, this streams stdout / stderr
   as commands execute, and returns the Process::Status return value
   upon completion (which has an exitstatus value)

puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb