Upgrade from 2.0.1 to 2.1.0 fails

[sdodsley]

When running the documented process for the plugin using Helm, the upgrade fails:

# helm upgrade pure-storage-driver pure/pure-k8s-plugin -f values.yaml --version 2.1.0 --recreate-pods

Error: UPGRADE FAILED: DaemonSet.apps "pure-flex" is invalid: spec.template.metadata.labels: Invalid value: map[string]string{"generator":"helm", "release":"pure-storage-driver", "app":"pure-flex", "chart":"pure-k8s-plugin", "date":"2018-07-31"}: selector does not match template labels && Deployment.apps "pure-provisioner" is invalid: spec.template.metadata.labels: Invalid value: map[string]string{"release":"pure-storage-driver", "app":"pure-provisioner", "chart":"pure-k8s-plugin", "date":"2018-07-31", "generator":"helm"}: selector does not match template labels

[patrick-east]

Fix for this is in #37