Fixes inability to stop or delete containers if DOCKER_ARGS used

# Problem

If you set `DOCKER_ARGS` to anything in `dvm.conf`, you will be unable to stop or delete containers. For an example of what happens, you can look over [this gist](https://gist.github.com/yacn/9195212#file-snipped_no_changes_output-txt).

With the changes in this pull request, this will no longer happen:

```
|ruby-1.9.3-p448| isaacs-air in ~/git/yacn/dvm/tmp
± |fix/unable-to-stop-delete-containers ✗| → mv ~/.dvm/{fixed_,}Vagrantfile
 
|ruby-1.9.3-p448| isaacs-air in ~/git/yacn/dvm/tmp
± |fix/unable-to-stop-delete-containers ✗| → dvm up
Bringing machine 'dvm' up with 'virtualbox' provider...
[dvm] Importing base box 'boot2docker-0.5.4-1'...
*vagrant SNIP*
[dvm] Running provisioner: shell...
[dvm] Running: inline script
boot2docker: 0.5.4
---> Configuring docker with args '-H unix:// -H tcp://' and restarting
 
|ruby-1.9.3-p448| isaacs-air in ~/git/yacn/dvm/tmp
± |fix/unable-to-stop-delete-containers ✗| → kitchen list
Instance Driver Provisioner Last Action
default-ubuntu Docker ChefZero <Not Created>
 
|ruby-1.9.3-p448| isaacs-air in ~/git/yacn/dvm/tmp
± |fix/unable-to-stop-delete-containers ✗| → kitchen create
-----> Starting Kitchen (v1.2.1)
-----> Creating <default-ubuntu>...
Step 0 : FROM ubuntu
Pulling repository ubuntu
*kitchen create SNIP*
Finished creating <default-ubuntu> (3m8.39s).
-----> Kitchen is finished. (3m8.43s)
 
|ruby-1.9.3-p448| isaacs-air in ~/git/yacn/dvm/tmp
± |fix/unable-to-stop-delete-containers ✗| → kitchen destroy
-----> Starting Kitchen (v1.2.1)
-----> Destroying <default-ubuntu>...
2118a87d5cf2f5d6bc502a3f086b4ab828e6c3023624e2da9e8590eae043ec1f
2118a87d5cf2f5d6bc502a3f086b4ab828e6c3023624e2da9e8590eae043ec1f
Finished destroying <default-ubuntu> (0m0.14s).
-----> Kitchen is finished. (0m0.20s)
 
|ruby-1.9.3-p448| isaacs-air in ~/git/yacn/dvm/tmp
± |fix/unable-to-stop-delete-containers ✗| → kitchen list
Instance Driver Provisioner Last Action
default-ubuntu Docker ChefZero <Not Created>
 
|ruby-1.9.3-p448| isaacs-air in ~/git/yacn/dvm/tmp
± |fix/unable-to-stop-delete-containers ✗| →
```

(you can view the full output [here](https://gist.github.com/yacn/9195212#file-raw_fixed_output-txt))

I used [this .kitchen.yml](https://gist.github.com/yacn/9195212#file-kitchen-yml) with [this dvm.conf](https://gist.github.com/yacn/9195212#file-dvm-conf) to confirm.