Could not build with kaniko when docker proxy with auth

### Expected behavior
Successful build

### Actual behavior
ImagePullBackOff in k8s cluster when skaffold build with kaniko

### Information

- Skaffold version: v1.35.2
- Operating system: MacOS
- Installed via: Homebrew
- Contents of skaffold.yaml:

```yaml
build:
artifacts:
- image:
kaniko:
dockerfile: build/Dockerfile
buildArgs:
BASE_IMAGE_NAME: "{{ .BASE_IMAGE_NAME }}"
cache: {}
cluster:
concurrency: 1
namespace: "default"
randomDockerConfigSecret: false
randomPullSecret: false
pullSecretName: pullsecret
dockerConfig:
path: dockerconfig.json
resources:
requests:
cpu: '200m'
memory: '500Mi'
limits:
cpu: '200m'
memory: '500Mi'
tagPolicy:
envTemplate:
template: "{{ or .IMAGE_TAG }}"
```

### Steps to reproduce the behavior

1. k8s cluster without internet for kanko build
2. docker proxy only able to get docker images
3. skaffold build
4. kubectl describe pod ...
ImagePullBackoff in status