(maint) Upgrade to latest puppet 8.x agents

[joshcooper]

On agents without package managers, we query builds to get the latest version. Now that puppet-agent-main-version is the latest puppet 9.x version, use puppet-agent-8.x-version instead. Also log what version is being used:

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    20  100    20    0     0     41      0 --:--:-- --:--:-- --:--:--    41
  Using latest puppet-agent-8.x 8.16.0.57.g2e9c77acb

[joshcooper]

I tested this using:

cd acceptance
export TEST_FRAMEWORK=beaker-rspec
export BEAKER_debug=true
export BEAKER_HOSTGENERATOR_VERSION='git@github.com:puppetlabs/beaker-hostgenerator-private.git#master'
export MASTER_COLLECTION=puppet8-nightly
export HOSTS=hosts.yaml
bundle install
bundle exec beaker-hostgenerator windows2012r2-64default.a-redhat9-64mdca --hypervisor abs > hosts.yaml
bundle exec rake ci
...
  Using latest puppet-agent-8.x 8.16.0.57.g2e9c77acb
...
      Debug: HTTP GET https://artifactory.delivery.puppetlabs.net/artifactory/internal_nightly__local/downloads/windows/puppet8-nightly/puppet-agent-8.16.0.57.g2e9c77acb-x64.msi returned 200 
...
    * (Agent) waiting for upgrade to complete...
      
      rich-department.delivery.puppetlabs.net (rich-department.delivery.puppetlabs.net) 11:30:58$ cat C:/ProgramData/PuppetLabs/puppet/cache/state/puppet_agent_upgrade.pid
        Trying command 1000 times.
      .      
      rich-department.delivery.puppetlabs.net (rich-department.delivery.puppetlabs.net) 11:30:58$ cat C:/ProgramData/PuppetLabs/puppet/cache/state/puppet_agent_upgrade.pid ostensibly successful.
    
    rich-department.delivery.puppetlabs.net (rich-department.delivery.puppetlabs.net) 11:30:58$ cmd.exe /c facter aio_agent_version
      8.16.0.57