Add logic to recognize when we are bringing a node under managememt.

When we first are, we want to kill any previous configuration.  Once
we know we manage a node, we will permit other interfaces to exist
outside our control.
Merge pull request #180 from VictorLowther/pull-req-release-pebbles-master-dd3666f0c95a7d5b43e788a8e2c8b5d2e1e2e7bd

Handle abandoning a nic when the network barclamp takes over a system. [3/4]