This adds a role convert-diskimage which uses the qemu-img tool to
convert diskimages from one format to another. Currently supported image
formats are raw and qcow2.
Change-Id: I4770af04c37f39e0cce23d5dd59ead744bed7d74
This adds a role variable to configure the diskimage-builder environment.
This allows users a choice of using the Ansible "environment" argument,
or using a variable. The variable may be particularly useful since it
allows full configuration of the role from a Zuul job definition.
Change-Id: I68542f13454b4f2e2e9bb8d356feefddba23d8f2
