Add support for NTLM to the Docker image

## To Reproduce

```
apt show gss-ntlmssp
```

## Observed Behavior

```
N: Unable to locate package gss-ntlmssp
```

## Expected behavior
```
apt show gss-ntlmssp
Package: gss-ntlmssp
Version: 0.7.0-4build3
Priority: optional
```

It would be useful to have the NTLM package installed for use with PowerShell remoting from Cloud Shell to Windows machines over WSMan.

## Additional context
See [this issue](https://github.com/PowerShell/PowerShell-Docker/issues/124) where the same request was made to the PowerShell Docker image.