Added a new check to the setup module that retrieves whether a net interface is on promiscuous mode

I have tested it against a Debian, an ubuntu and a Fedora system. I haven't tested it against a BSD like system. I think maybe on a BSD-like system the ethernet card information is located in a different place.

Systems in which it has been tested:
Linux ubuntu 3.8.0-29-generic #42~precise1-Ubuntu SMP Wed Aug 14 16:19:23 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

Linux devel 3.9-1-amd64 #1 SMP Debian 3.9.6-1 x86_64 GNU/Linux

Fedora 18: Linux localhost.localdomain 3.6.10-4.fc18.i686 #1 SMP Tue Dec 11 18:24:49 UTC 2012 i686 i686 i386 GNU/Linux