Failed to get resources ready failing with webhook.

[vaikas]

Describe the bug
Last few continuous test failures have been of the form:

https://prow.knative.dev/view/gcs/knative-prow/logs/ci-knative-eventing-continuous/1288276236098867200

    operation.go:108: Failed to get all test resources ready: failed waiting for {TypeMeta:{Kind:Subscription APIVersion:messaging.knative.dev/v1} ObjectMeta:{Name:e2e-channelchain-subs11 GenerateName: Namespace:test-channel-chain-channel-messaging-knative-dev-v1-2256f SelfLink: UID: ResourceVersion: Generation:0 CreationTimestamp:0001-01-01 00:00:00 +0000 UTC DeletionTimestamp:<nil> DeletionGracePeriodSeconds:<nil> Labels:map[] Annotations:map[] OwnerReferences:[] Finalizers:[] ClusterName: ManagedFields:[]}} to become ready: conversion webhook for messaging.knative.dev/v1beta1, Kind=Subscription failed: Post https://eventing-webhook.knative-eventing-gwsw4v429g.svc:443/resource-conversion?timeout=30s: EOF

And:
https://prow.knative.dev/view/gcs/knative-prow/logs/ci-knative-eventing-continuous/1288397032322502656

    operation.go:108: Failed to get all test resources ready: failed waiting for {TypeMeta:{Kind:Subscription APIVersion:messaging.knative.dev/v1} ObjectMeta:{Name:e2e-eventtransformation-subs22 GenerateName: Namespace:test-event-transformation-for-subscription-v1-channel-messw9sx6 SelfLink: UID: ResourceVersion: Generation:0 CreationTimestamp:0001-01-01 00:00:00 +0000 UTC DeletionTimestamp:<nil> DeletionGracePeriodSeconds:<nil> Labels:map[] Annotations:map[] OwnerReferences:[] Finalizers:[] ClusterName: ManagedFields:[]}} to become ready: conversion webhook for messaging.knative.dev/v1beta1, Kind=Subscription failed: Post https://eventing-webhook.knative-eventing-e2yxzzfx3t.svc:443/resource-conversion?timeout=30s: EOF

knative/pkg#1509

Expected behavior
Tests to pass continuously

To Reproduce
Steps to reproduce the behavior.

Knative release version

Additional context
Add any other context about the problem here such as proposed priority

[vaikas]

Looks like both of these flaked with this issue here:
#3442