Delete unused interfaces.control key.

Change-Id: I3a84cf52cc46f0c338319a046d77edb2a9b29c45
Make neutron public interface configurable.

Not all machines use eth0 :).

Change-Id: I2d0cfd8df46e7eda1b7db2ea5c8e84d3e970c862
Make it possible to set the public interface ip.

This is already supported by the ovs agent, but we didn't need it for
the emulated overclouds. Now we're working on bare metal, it's needed
for some deployments.

Change-Id: Ibb41c40d371e4c153a84fd09c370b158add75b81