Support custom NetBIOS domain names

[Joytide]

Description

The screenshot below shows the issue I ran into: LDAP GPC retrieval was working, but the embedded SMB server was unable to establish the Netlogon secure channel and kept returning:

The issue was that the AD domain's NetBIOS name did not match the first part of its DNS name.

In my case:

DNS domain:     corp.com
NetBIOS domain: CORPCOM

OUned currently does not pass DOMAIN_NB_NAME when creating Scapy's NTLMSSP_DOMAIN, so Scapy falls back to:

DOMAIN_FQDN.split(".")[0].upper()[:15]

In the example above, it will assumes CORP instead of the actual CORPCOM, which causes the Netlogon authentication to fail.

Changes

This PR adds an optional domain-netbios setting:

# Required if domain=corp.com but nETBIOSName=CORPCOM (default is CORP)
#domain-netbios=corpcom

When set, it's passed to Scapy as DOMAIN_NB_NAME.

When it's not set, it simply passes None and Scapy keeps its current fallback behavior.