s3-krb5 Fix Kerberos on FreeBSD with Samba4 DCs

s3-krb5 Fix Kerberos on FreeBSD with Samba4 DCs

The idea of this patch is: Don't support a mix of different kerberos
features.

Either we should prepare a GSSAPI (8003) checksum and mark the request as
such, or we should use the old behaviour (a normal kerberos checksum of 0 data).

Sending the GSSAPI checksum data, but without marking it as GSSAPI broke
Samba4, and seems well outside the expected behaviour, even if Windows accepts it.

Andrew Bartlett