Use Start-Job with -ArgumentList

Signed-off-by: Stefan Scherer <scherer_stefan@icloud.com>

scripts/docker/docker-pull-async.ps1

-function DockerPull {
-  Param ([string]$image)
-
-  Write-Host Installing $image ...
-  $j = Start-Job -ScriptBlock { docker pull $image }
-  while ( $j.JobStateInfo.state -ne "Completed" ) {
-    Write-Host $j.JobStateInfo.state
-    Start-Sleep 10
-  }
-
-  $results = Receive-Job -Job $j
-  $results
-}
-
-DockerPull microsoft/windowsservercore
-DockerPull microsoft/nanoserver
+function DockerPull {
+  Param ([string]$image)
+
+  Write-Host Installing $image ...
+  $j = Start-Job -ScriptBlock { docker pull $args[0] } -ArgumentList $image
+  while ( $j.JobStateInfo.state -ne "Completed" ) {
+    Write-Host $j.JobStateInfo.state
+    Start-Sleep 10
+  }
+
+  $results = Receive-Job -Job $j
+  $results
+}
+
+DockerPull microsoft/windowsservercore
+DockerPull microsoft/nanoserver