periodic.conf(5): don't truncate interface names reported by 420.status-network.

The daily periodic script, 420.status-network uses netstat(1) to report
interface status. By default, netstat(1) truncates interface names.

Add the '-W' flag (avoid truncating interface names) as the default for
'daily_status_network_netstat_flags' in periodic.conf(5).

The default 420.status-network command is now 'netstat -i -d -W -n'.

PR: 163572
Reported by: kes-kes@yandex.ru
Reviewed by: allanjude (mentor) bcr (manpages)
Approved by: allanjude (mentor)
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D26023