Avoid merge collision with PodSpec arrays
Avoid merge collision with PodSpec arrays

Given:
```json
{
  "volumes": [
    {"name": "pach-bin", "emptyDir": {}}
  ]
}
```

And applying patch:
```json
[
  {
    "op": "add",
    "path": "/volumes/0",
    "value": {
      "name": "my-volume",
      "hostPath": {
        "path": "/hello"
      }
    }
  }
]
```

In the existing code, one would end up with:
```json
{
  "volumes": [
    {"name": "my-volume", "emptyDir": {}, "hostPath": {"path": "/hello"}}
  ]
}
```

pachyderm/pfs,pachyderm/pfs,pachyderm/pfs