Add support to launch node for attaching volumes

We are using cinder block devices more and more. Update launch node so
that it can attach a preexisting cinder volume against a new nova server
on first boot. This will allow puppet or other config management to
format and mount that block device into the VMs filesystem.

Change-Id: Ic121cdc06dcbea0e38e8d0ff8946e999af3d727e
Merge "Add support to launch node for attaching volumes"