Evaluate the necessity of Microsoft-specific NCSI DNS record

[sebschrader]

We should verify if the following DNS record in unauth-dnsmasq.conf for the Microsoft Windows Network Connection Status Indicator (NCSI) is really necessary.

This was added to let Windows detect the presence of the captive portal. But it seems that some machines still try to obtain Windows updates, although the captive portal is present.

For more background information see this superuser blog entry and this technet blog entry