Kernel not respecting extensions/configuration

I'm having trouble getting configuration specified to a kernel launched by the notebook server. I've put configuration instructions in both `~/.ipython/profile_default/ipython_kernel_config.py` and `~/.ipython/profile_default/ipython_config.py` (and symlinked `~/.config/ipython` -> `~/.ipython`, just in case) with no success. Contents of the config file are:

```python
c.InteractiveShellApp.extensions = ['dask_extension']
c.InteractiveShellApp.reraise_ipython_extension_failures = True
```

I've proven these files are opened and read by using strace in front of the ipython kernel command (`
strace -o oot.txt ipython kernel -f /run/user/1001/jupyter/.json`), but the extension is not loaded on startup, nor can I find where this configuration even goes.

Inside of the notebook itself, I have a cell:

```python
i=get_ipython()
i.extension_manager.loaded
```

which gives the default extensions:

```python
{'ipywidgets', 'storemagic'}
```

Trying to inspect the configuration (`i.config`) only gives:

```python
{'IPKernelApp': {'connection_file': '/run/user/1001/jupyter/kernel-f6ea9e24-9d6b-4f32-b937-dbbd995cd7ea.json'}}
```

In fact, any object with a config only gives this result.

The extension is loadable with `%load_ext dask_extension` or `i.extension_manager.load_extension('dask_extension')`, so it's not an issue with not being able to find the extension.

What am I missing here? Why does this configuration seems to disappear?