This makes use of the dhcpcd package and it's ability to run on all
interfaces by default. We disable the privacy extensions and dhcp
overriding the hostname (both are enabled by default). Other than
that it 'just works' and was the method used to bring up interfaces
on Gentoo Openstack images before we switched to building with DIB.
Change-Id: I02c14927d70b22f560c6fc149fefca0f93933f56
