s3:smbd: try to make fsp->fh->gen_id as globally unique as possible

s3:smbd: try to make fsp->fh->gen_id as globally unique as possible

This makes sure the value is never 0, it's between 1 and UINT32_MAX.

While fsp->fh->gen_id is 'unsigned long' currently (which might by 8 bytes),
there's some oplock code which truncates it to uint32_t (using IVAL()).

Which means we could reuse fsp->fh->gen_id as persistent file id
until we have a final fix, which uses database.

See bug #8995 for more details.

Based on code from Ira Cooper. Ensure fsp->fh->gen_id starts from
a random point. We will use this as the SMB2 persistent_id.

metze

Signed-off-by: Jeremy Allison <jra@samba.org>