This is a stable-2.4 follow-up task for #2498 (comment). In stable-2.3, we have decided to postpone the support of overriding configs for existing CLI-injected workloads, due to reasons described in the above comment and #2576.

The focus of this task is to ensure that following #2576, the configs override of existing CLI-injected workloads work. Depending on the implementation decision of #2576, if the proxy spec is removed from the output of linkerd inject, then no changes to the webhook will be necessary, as the webhook will pick up the pod (during CREATE) and mutate its pod spec to include the proxy container.