docker: fix targetting images by name

Say you have the following images:

```
$ docker ps -a
CONTAINER ID   IMAGE                            COMMAND     CREATED       STATUS       PORTS   NAMES
4821bfe5d3f1   localhost:5000/my_image:latest   /bin/bash   2 hours ago   Up 2 hours           my_container_1
0f6cf245c7fa   localhost:5000/my_image:latest   /bin/bash   2 hours ago   Up 2 hours           my_container_2
4ed6cdb0a903   localhost:5000/my_image:latest   /bin/bash   2 hours ago   Up 2 hours           my_container_3

```

and a playbook:

```
---
- hosts: all
- tasks:
  - docker:
      image: localhost:5000/my_image:latest
      name: my_container_4
      state: absent
```

Before this patch, running this playbook would cause `my_container_{1,2,3}` to be removed, which is not expected.  With this patch, only `my_container_4` is removed, if present.