Fix Windows slave bootstrap script
For tensorflow tests, we install pyreadline package by pip.
But pip won't be available until anaconda3 installation is completed.
@@ -46,7 +46,7 @@ $anaconda3_tmp_folder = "c:\temp\anaconda3"
New-Item $anaconda3_tmp_folder -type directory -force
$anaconda3_installer = $anaconda3_tmp_folder + "\Anaconda3-4.2.0-Windows-x86_64.exe"
(New-Object Net.WebClient).DownloadFile("https://repo.continuum.io/archive/Anaconda3-4.2.0-Windows-x86_64.exe", $anaconda3_installer)
-& $anaconda3_installer /AddToPath=0? /InstallationType=AllUsers /S /D='C:\Program Files\Anaconda3'
+Start-Process -Wait $anaconda3_installer -ArgumentList "/AddToPath=0? /InstallationType=AllUsers /S /D='C:\Program Files\Anaconda3'"
# Install pyreadline (Windows-compatible Python GNU readline library).
# Required by TensorFlow Python tests (tfdbg).
