store etcd data in a persistent volume

[Ricardo Rocha]

In principle a multi instance etcd service does not require persistency for its storage.

But on a cluster with a single master, no LB setup, allowing the etcd storage to be put in a persistent volume opens up the possibility of upgrading the master (including the instance image) by doing a simple nova rebuild. Both the IP and the etcd data would be preserved, with minimum downtime for the cluster APIs.

To cover this use case, we should add an option to the cluster creation where users can specify the size of the volume for the etcd storage. Default should stay 0, which means no persistent volume should be created and the local instance disk is used as happens today.

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/473789

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/480536

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/473789
Committed: https://git.openstack.org/cgit/openstack/magnum/commit/?id=2875c97bff9fe46a2f56f12adff28d7c3e0c2cec
Submitter: Jenkins
Branch: master

commit 2875c97bff9fe46a2f56f12adff28d7c3e0c2cec
Author: Ricardo Rocha <email address hidden>
Date: Tue Jun 13 11:19:38 2017 +0000

    k8s-fedora: Add etcd_volume_size label

    Allow setting the size of a volume for etcd storage.

    Default is 0 which matches the current behavior - no persistency.

    Related-Bug: #1697655

    Change-Id: I8a30df63684133a902ae209ba6c124da2a567d3f

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/480536
Committed: https://git.openstack.org/cgit/openstack/magnum/commit/?id=eba956061bcf595ed392bd0da26774677d6a5df0
Submitter: Jenkins
Branch: master

commit eba956061bcf595ed392bd0da26774677d6a5df0
Author: Ricardo Rocha <email address hidden>
Date: Wed Jul 5 11:48:01 2017 +0000

    Add reno for etcd_volume_size label

    Related-Bug: #1697655

    Change-Id: I2755c0b365a4b0c77d486cd478cc0ceefe381030