fix autostart winrm service, blank after equal sign required

The WinRM autostart command had a typo, so the service still starts after booting the guest, but it will be started delayed (after 120 seconds). So using such boxes with vagrant results in a slow login with vagrant-windows plugin.
I have compared both the winrm script in [basebox-packer](https://github.com/misheska/basebox-packer) repo
where the typo is already fixed 2 months ago.

In the command 
```
cmd.exe /c sc config winrm start= auto
```
there must be a space after the equal sign.