Allow additional flags to be passed to netstat -i in the daily status check.
In particular, this allows an administrator to specify "-h" for human
readable output if that is preferred.

The default setting passes "-d", so that can be excluded by using a custom
setting.

Differential Revision: https://reviews.freebsd.org/D2034
Submitted by: Lystopad Aleksandr <laa@laa.zp.ua>

		(patch to add option for -h)

Reviewed by: bz
MFC after: 1 week