(MODULES-10653) Failed to upgrade agent using puppet task

Before this commit, when trying to run the
`puppet_agent::install_powershell` task, with a specific version as
parameter, it was failing with below error message:
Error: Timed out waiting for status response from <node_name>

On the node, both `puppet agent` and `pxp-agent` services got stopped
and the event log viewer showed:
Application or service 'task_wrapper' could not be shut down.

Due to Windows agents becoming unresponsive when running this task and
as per MODULES-10633 discussions, the `puppet_agent::install_poweshell`
task should not be used for upgrading Puppet Agents while either of
`puppet agent` or `pxp-agent` services are still running. This Puppet
Agent module task will now fail immediately and output a message if any
of the two affected services are still runnning.

The task will stop and output a message if the given version is already
installed on the node, thus avoiding unnecessary msi
download/installation. This behaviour is aligned with the existing
implementation for no version given and Puppet Agent already installed
on the node.

Author: luchihoratiu

tasks/install_powershell.ps1

@@ -34,7 +34,45 @@ function Test-PuppetInstalled {
   }
 }
 
+function Test-PuppetInstalledVersion {
+  $rootPath = 'HKLM:\SOFTWARE\Puppet Labs\Puppet'
+
+  $reg = Get-ItemProperty -Path $rootPath -ErrorAction SilentlyContinue
+  if ($null -ne $reg) {
+    if ($null -ne $reg.RememberedInstallDir64) {
+      $loc = $reg.RememberedInstallDir64+'VERSION'
+    } elseif ($null -ne $reg.RememberedInstallDir) {
+      $loc = $reg.RememberedInstallDir+'VERSION'
+    }
+  }
+
+  if ($null -ne $loc) {
+    $installedVersion = Get-Content -Path $loc -ErrorAction SilentlyContinue
+    if ($installedVersion -eq $version) {
+      RETURN $true
+    }
+  }
+
+  RETURN $false
+}
+
+function Test-RunningServices {
+  $puppetAgentService = Get-Service -DisplayName 'Puppet Agent' -ErrorAction SilentlyContinue
+  $pxpAgentService = Get-Service -DisplayName 'Puppet PXP Agent' -ErrorAction SilentlyContinue
+
+  if ($puppetAgentService.Status -eq 'Running' -or $pxpAgentService.Status -eq 'Running') {
+    RETURN $true
+  }
+
+  RETURN $false
+}
+
 if ($version) {
+    if (Test-PuppetInstalledVersion) {
+      Write-Output "Puppet Agent version $version is already installed on $env:COMPUTERNAME. Nothing to do."
+      Exit
+    }
+
     if ($version -eq "latest") {
       $msi_name = "puppet-agent-${arch}-latest.msi"
     } else {
@@ -50,6 +88,10 @@ else {
     $msi_name = "puppet-agent-${arch}-latest.msi"
 }
 
+if (Test-RunningServices) {
+  Write-Error "Puppet Agent upgrade cannot be done while Puppet services are still running."
+}
+
 # Change windows_source only if the collection is a nightly build, and the source was not explicitly specified.
 if (($collection -like '*nightly*') -And -Not ($PSBoundParameters.ContainsKey('windows_source'))) {
   $windows_source = 'https://nightlies.puppet.com/downloads'