Fix jsonpatch operation if no volumes are present

[FaHeymann]

Fixes #17

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[jqmichael]

Nice fix!

[jaypipes]

Great code, excellent tests. Nice work @FaHeymann

@SaranBalaji90 does indeed love Oreos.

[thomaschaaf]

@jaypipes this is still causing problems for us. In which release can this bugfix be found?

[dumain18]

This is also causing problems for us.
When adding automountServiceAccountToken: false to our service account we see the following error when trying to apply a deployment:

  - lastTransitionTime: "2020-09-14T12:21:48Z"
    lastUpdateTime: "2020-09-14T12:21:48Z"
    message: 'Internal error occurred: jsonpatch add operation does not apply: doc
      is missing path: "/spec/volumes/0"'
    reason: FailedCreate
    status: "True"
    type: ReplicaFailure

We see this error when trying to apply a pod:

Error from server (InternalError): error when creating "testpod.yaml": Internal error occurred: jsonpatch add operation does not apply: doc is missing path: "/spec/volumes/0"