ITL: Add option for ifName to Manubulon CheckCommand 'snmp_interface'

ITL: Add option for ifName to Manubulon CheckCommand 'snmp_interface'

Recent Net-SNMP's snmpd daemon has changed behavior returning detailed
information about the network interfaces in the IF-MIB::ifDescr MIB.

There is a patch out there that is working around the issue (see also
https://bugs.debian.org/812837) by providing the behaviour via '-N'.

This path provides a way to make use of this workaround.

fixes #11931

Signed-off-by: Michael Friedrich <michael.friedrich@netways.de>