Set locations of ifup and ifdown as string var for implifcfg

OK - so ideally I'd like to move these definitions to NetConfig (because it's the same for ubuntu) but couldn't quickly get it to work. Have bigger fish to fry working out https://github.com/marios/os-net-config/commit/585052484a0e859844b2551ddfc1d29ffac5f53e - will get back to you on that in next couple days,

thanks! marios