bug 1030276 - Display JSON processor output in Raw Dump tab

```python
>>> d={"a": {"A": "foo"}}
>>> x=dict(d)
>>> x
{'a': {'A': 'foo'}}
>>> x['a']['A'] = 'bar'
>>> d
{'a': {'A': 'bar'}}
```
If you really need to to this, use `copy.deepcopy()`
```python
>>> import copy
>>> d
{'a': {'A': 'bar'}}
>>> y=copy.deepcopy(d)
>>> y['a']['A'] = 'foobar'
>>> d
{'a': {'A': 'bar'}}
```

But is it really necessary? The `context['report']['json_dump']` isn't used for anything else later down in the view, is it? Especially not the `sensitive` key. And if so, we're doing a good deed deleting it early anyway. 

I'm bringing this up because calling `copy.deepcopy()` is rather expensive'ish and best avoided if possible.