Precision about failedPrecondition as final error

[guilhem]

Following #53 and #54

According to CSI spec, a volume published to another node should report FAILED_PRECONDITION even if change is underway.
https://github.com/container-storage-interface/spec/blob/98819c45a37a67e0cd466bd02b813faf91af4e45/spec.md?plain=1#L1384

external-attacher will consider it as a final error, is it the behavior we want?

[jsafrane]

I'm not sure I understand the concern. My interpretation of FAILED_PRECONDITION returned to ControllerPublishRequest with {"node_id": "node_A"} means that the volume cannot be being attached to node_A, because it's attached to another node. And thus we can consider it final.