(PA-8247) Add guard against other ruby process when installing

Previously, when installing puppet on Windows, if there is
another already running ruby.exe process running during the
install, it would fail with an `msiexec 1603` error:

	Error: Failed previous installation with: ScriptHalted MSI (s)
        (60:6C) [22:12:51:748]: Product: Puppet Agent (64-bit) -- Error
        1306. Another application has exclusive access to the file
        'C:\Program Files\Puppet Labs\Puppet\puppet\bin\ruby.exe'.
        Please shut down all other applications, then click Retry.
        ...
        ERROR: msiexec.exe installation failed!!! Return code 1603

This commit updates files/install_puppet.ps1 to guard against
other ruby processes by waiting for it to finish before trying
to install puppet. It will wait however long `$WaitForPuppetRun` is
before erroring.

Author: AriaXLi

files/install_puppet.ps1

@@ -320,6 +320,30 @@ try {
     $msi_arguments += " PUPPET_AGENT_STARTUP_MODE=`"$PuppetStartType`""
   }
   $msi_arguments += " $InstallArgs"
+
+  # Check & wait for other ruby process to end 
+  # This ensures no other ruby.exe processes are running before installing
+  if ($InstallDir) {
+    $escapedInstallDir = $InstallDir -replace '\\', '\\'
+  }
+  if (Test-Path "$escapedInstallDir\puppet\bin\ruby.exe") { # The first time an upgrade is run with InstallDir, ruby.exe will not yet exist there yet
+    $other_ruby_process_id = Get-CimInstance Win32_Process -Filter "Name='ruby.exe' AND ExecutablePath LIKE '$escapedInstallDir\\puppet\\bin\\ruby.exe'" | Select-Object -First 1 -ExpandProperty ProcessID
+  } else {
+    $other_ruby_process_id = Get-CimInstance Win32_Process -Filter "Name='ruby.exe' AND ExecutablePath LIKE 'C:\\Program Files\\Puppet Labs\\Puppet\\puppet\\bin\\ruby.exe%'" | Select-Object -First 1 -ExpandProperty ProcessID
+  }
+  if ($other_ruby_process_id) {
+    Write-Log "Waiting for other ruby process to stop, PID: $other_ruby_process_id" $Logfile
+    $ruby_process = Get-Process -ID $other_ruby_process_id -ErrorAction SilentlyContinue
+    if ($ruby_process) {
+      if (!$ruby_process.WaitForExit($WaitForPuppetRun)){
+        Write-Log "ERROR: Timed out waiting for ruby!" $Logfile
+        throw
+      }
+    } else {
+      Write-Log "Ruby already finished" $Logfile
+    }
+  }
+
   Write-Log "Beginning MSI installation with Arguments: $msi_arguments" $Logfile
   Write-Log "****************************** Begin msiexec.exe output ******************************" $Logfile
   $startInfo = New-Object System.Diagnostics.ProcessStartInfo('msiexec.exe', $msi_arguments)