smbd: get a valid file stat to disk_quotas

smbd: get a valid file stat to disk_quotas

Most calls to disk_quotas originate at a state with an
open file descriptor. Pass the file's stat info down to
disk_quota, so that we can avoid extra stat's and the related
error handling.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12145

Signed-off-by: Uri Simchoni <uri@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>