Docker image doesn't support glob syntax

### Description

The docker image for kubeval doesn't expand glob syntax making it impossible to properly scan complex directory structures that have been mounted into the container.

### Expected Outcome

```sh
$ docker run -it -v $PWD/environments:/environments garethr/kubeval "/environments/**/*.yaml"
The document /environments/test1/config.configmap.yaml contains a valid ConfigMap
The document /environments/test2/config.configmap.yaml contains a valid ConfigMap
```

### Actual Outcome

```sh
$ docker run -it -v $PWD/environments:/environments garethr/kubeval "/environments/**/*.yaml"
Could not open file /environments/**/*.yaml
```

### Environment

`garethr/kubeval@sha256:6693cb13212d8bee7fd028e7f074be569c59d369d77e58fbaef231e46342aa6c`