Fix ceph-secret type to kubernetes.io/rbd in kubernetes-master charm

[Cynerva]

What this PR does / why we need it:

This fixes the type of the ceph-secret secret that's created by the kubernetes-master charm.

Without the kubernetes.io/rbd type, automatic provisioning of PVCs doesn't work.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

Release note:

Fix ceph-secret type to kubernetes.io/rbd in kubernetes-master charm

[k8s-reviewable]

This change is 

[k8s-ci-robot]

Hi @Cynerva. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with @k8s-bot ok to test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[Cynerva]

/assign @chuckbutler

I believe you were around when our ceph operational code was originally added. Can you review this change?

[lazypower]

This is +1 LGTM. I had no clue this was a schema type. looking at https://github.com/kubernetes/kubernetes/tree/master/examples/persistent-volume-provisioning i see this is clearly outlined. Thanks for the fix @Cynerva

[lazypower]

/approve

[lazypower]

/lgtm

[k8s-github-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Cynerva, chuckbutler

Needs approval from an approver in each of these OWNERS Files:

• cluster/juju/OWNERS [chuckbutler]

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[lazypower]

@k8s-bot unit test this

[k8s-github-robot]

Automatic merge from submit-queue