Mimic Docker CLI behavior when running an image using  "hostname" parameter

Running and image with the docker module from Ansible results in different container information as if the same image was run using Docker CLI.

An example, running any image from Ansible like this:

```    
- name: run container
      docker:
        image: "ubuntu"
        hostname : host.mydomain.com
        command : "/bin/echo hello world"  
```
and then checking the container information created in Docker (```    docker inspect **container_id** | grep "Hostname\|Domainname" ```    ) gives this:

```    
        "Domainname": "",
        "Hostname": "host.mydomain.com",
```    

while doing the same thing using the Docker CLI:
```    
docker run --hostname  host.mydomain.com ubuntu /bin/echo hello world
```    
results in:
```    
        "Domainname": "mydomain.com",
        "Hostname": "host",
```    

I have changed the module so that it splits the **hostname** in **hostname** and **domainname** and passes them as params to the Docker python client to fix it.