s4/dns_server: prepare sending correct error responses for dns_verify_tsig() errors

s4/dns_server: prepare sending correct error responses for dns_verify_tsig() errors

Call dns_verify_tsig() after updating state.flags and assign and use
out_packet for dns_verify_tsig().

We will need the updated flags when sending TSIG error responses when
TSIG request MAC verification fails and dns_verify_tsig() uses the
passed in packet as response, so we have to make sure we copy in_packet
to out_packet before calling out and pass out_packet.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>