smbd: Remove the ZERO_ZERO define

smbd: Remove the ZERO_ZERO define

This code went in with e8e98c9ea06 in 2001 without any mention in the
commit message.

I don't remember all details, but there was some discussion around the
offset=0,length=0 lock being somehow special. These days [MS-FSA]
defines the required behaviour (don't conflict) and we implement that
behaviour.

If someone still remembers why this code is in and thinks it's
worthwhile, that's what version control is for.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>