linkerd upgrade not updating proxy image versions #2660
Description
Summary
The linkerd upgrade command is incorrectly persisting gcr.io/linkerd.io/proxy and gcr.io/linkerd.io/proxy-init version tags.
Symptom
Upgrading from edge-19.3.2 to edge-19.4.2 yields a broken control-plane:
$ kubectl -n linkerd logs -f $(kubectl -n linkerd get po --selector=linkerd.io/control-plane-component=web -o jsonpath='{.items[*].metadata.name}') -c linkerd-proxy
ERR! linkerd2_proxy::app::config LINKERD2_PROXY_POD_NAMESPACE is not set
configuration error: InvalidEnvVarRepro
$ export LINKERD2_VERSION=edge-19.3.2 && curl https://run.linkerd.io/install-edge | sh
...
$ linkerd install | kubectl apply -f -
...
$ linkerd version
Client version: edge-19.3.2
Server version: edge-19.3.2$ bin/linkerd version
Client version: edge-19.4.2
Server version: edge-19.3.2
$ bin/linkerd upgrade|grep "image: gcr.io/linkerd.io/proxy"
√ You're on your way to upgrading Linkerd!
Visit this URL for further instructions: https://linkerd.io/upgrade/#nextsteps
image: gcr.io/linkerd-io/proxy:edge-19.3.2
image: gcr.io/linkerd-io/proxy-init:edge-19.3.2
image: gcr.io/linkerd-io/proxy:edge-19.3.2
image: gcr.io/linkerd-io/proxy-init:edge-19.3.2
image: gcr.io/linkerd-io/proxy:edge-19.3.2
image: gcr.io/linkerd-io/proxy-init:edge-19.3.2
image: gcr.io/linkerd-io/proxy:edge-19.3.2
image: gcr.io/linkerd-io/proxy-init:edge-19.3.2
image: gcr.io/linkerd-io/proxy:edge-19.3.2
image: gcr.io/linkerd-io/proxy-init:edge-19.3.2