Consul Connect must route traffic between network namespaces through a
public interface (i.e. not localhost). In order to support testing in
dev mode, users needed to manually set the interface which doesn't
make for a smooth experience.
This commit adds a facility for adding optional parameters to the
`nomad agent -dev` flag and uses it to add a `-dev=connect` flag that
binds to a public interface on the host.
Tim Gross