Run all tests as root 96

fixes #96 
I also notice that the temp path generated by this code is eg `/tmp/flocker.volume.functional.test_s/FlockerVolumeTests/test_no_permission/`

It would be better if you used a unique identifiable root within /tmp eg

`/tmp/flocker_test_temp.<PID>/flocker.volume.functional.test_s...`

You could do that using something like:
```
In [44]: FilePath(tempfile.gettempdir()).child('flocker_test_temp').siblingExtension('.{}'.format(os.getpid()))
Out[44]: FilePath('/tmp/flocker_test_temp.14119')
```

But then you'd need to clean up old tmp dirs too, which could be done as a first step using:

```
In [78]: while True:
   ....:     d=FilePath(tempfile.gettempdir()).child('flocker_test_temp').siblingExtensionSearch('*')
   ....:     if d:
   ....:         d.remove()
   ....:     else:
   ....:         break
   ....:   
```