Revert "s4-netlogon: always set the dNSHostName in GetDomainInfo"

Revert "s4-netlogon: always set the dNSHostName in GetDomainInfo"

This reverts commit 87b6f2e863c6e117643ab6704e50167e849b69cc.

This was the cause of the breakage of the "LogonGetDomainInfo" testsuite. I
think my behaviour is more correct to Windows Server since the test works
against it (at least release 2003 R2).

One problem I discovered is that freshly joined workstations don't get their
DNS name into the directory. Therefore I think also another part (maybe another
RPC call) is able to do this.