Comment 2 for bug 1820289

Reviewed: https://review.openstack.org/643507
Committed: https://git.openstack.org/cgit/openstack/tripleo-heat-templates/commit/?id=745369e8ac77f84f03ad7498b112888392ee094d
Submitter: Zuul
Branch: stable/rocky

commit 745369e8ac77f84f03ad7498b112888392ee094d
Author: Giulio Fidente <email address hidden>
Date: Sat Jan 19 10:23:23 2019 +0100

    Enable Glance image_conversion plugin when backend is rbd

    Ceph can store QCOW2 images but to be able to create Nova guests
    from image snapshots the image format must be in RAW format,
    otherwise Nova will download the QCOW2 image, convert it locally
    and upload it back into the Ceph pool if the ephemeral storage is
    also Ceph. This process slows down guest boot especially when
    multiple guests are booted in parallel and consumes a lot of CPU
    and network resources.

    This change enables the Glance image_conversion plugin when the
    Glance backend is set to 'rbd', which takes care of converting
    the uploaded images into RAW format automatically when operators
    use the glance 'import' command.

    Conflicts:
           puppet/services/glance-api.yaml

    Closes-bug: #1820289
    Change-Id: I9fc0758dbe64f3fcf0e990f4253151e9472a6ab6
    (cherry picked from commit ccb242f919a09527ec8414b95dda65e390cab9a2)