smbd: implement the strange write time update logic

smbd: implement the strange write time update logic

We now never call file_ntimes() directly, every update
is done via smb_set_file_time().

This let samba3 pass the BASE-DELAYWRITE test.

The write time is only updated 2 seconds after the
first write() on any open handle to the current time
(not the time of the first write).

Each handle which had write requests updates the write
time to the current time on close().

If the write time is set explicit via setfileinfo or setpathinfo
the write time is visible directly and a following close
on the same handle doesn't update the write time.

metze