As a work-around, I've noticed on the B+ that if you keep the Ethernet disconnected until it booting and then connect it when you see it hit "... Networking" then it'll pick up DHCP and then run cloud-init next happily.
As a work-around, I've noticed on the B+ that if you keep the Ethernet disconnected until it booting and then connect it when you see it hit "... Networking" then it'll pick up DHCP and then run cloud-init next happily.