[oe] [meta-networking] postfix: permissions on the /var/spool/mail seems incorrect

[Zhenbo Gao]

Hi Joe MacDonald,

I am confused with the permission on /var/spool/mail of the postfix recipe, 
why it is set to 2755?

See the following output:
root at qemu0:~# rpm -qlv postfix | grep /var/spool/mail
drwxr-sr-x 2 postfix nogroup 0 Sep 8 08:46 /var/spool/mail

The premission of /var/spool/mail ("r-s") seems strange as it
belongs to nogroup, i think it is better to modify it to 0755
as to the normal case.

If so, the patch is offered.
If not, Can you give some advice?

Thanks,
Zhenbo