Retry after five seconds

scripts/vm-guest-tools.bat

 if not exist "C:\Windows\Temp\7z920-x64.msi" (
     powershell -Command "(New-Object System.Net.WebClient).DownloadFile('http://www.7-zip.org/a/7z920-x64.msi', 'C:\Windows\Temp\7z920-x64.msi')" <NUL
 )
+if not exist "C:\Windows\Temp\7z920-x64.msi" (
+    powershell -Command "Start-Sleep 5 ; (New-Object System.Net.WebClient).DownloadFile('http://www.7-zip.org/a/7z920-x64.msi', 'C:\Windows\Temp\7z920-x64.msi')" <NUL
+)
 msiexec /qb /i C:\Windows\Temp\7z920-x64.msi
 
 if "%PACKER_BUILDER_TYPE%" equ "vmware-iso" goto :vmware