daemon: MoveEthernetDevice moves ethernet devices from one container to another.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
execdriver: Support multiple interfaces (do not add them yet)

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)