Make utility work in the face of 2 issues found on Ubuntu 16.04#44

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nitsanw wants to merge 3 commits intomkorenkov:masterfrom

Commits on Sep 28, 2016

Fix for resource busy, and also for machines where the interface id is 2 instead of 0. I expect this will break it for people who don't suffer from this issue.
nitsanw
committed
handle old/new interface numbers
nitsanw
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Nicer messages
nitsanw
committed