Fix docker's list_containers function

[johnnyWalnut]

add an extra check otherwise list_containers breaks with AttributeError

Fix function list_containers for docker

Description

I tested locally docker's list_containers(), which was expected to return a list of containers.
But i ended up with this

<ipython-input-5-34990fe7ad41> in <module>()
----> 1 con.list_containers()

/home/johnny/Documents/mylibcloud/env/src/fork_libcloud/libcloud/libcloud/container/drivers/docker.py in list_containers(self, image, all)
    301             raise
    302 
--> 303         containers = [self._to_container(value) for value in result]
    304         return containers
    305 

/home/johnny/Documents/mylibcloud/env/src/fork_libcloud/libcloud/libcloud/container/drivers/docker.py in _to_container(self, data)
    622                 name = data.get('Names')[0].strip('/')
    623             except:
--> 624                 name = data.get('Id')
    625         state = data.get('State')
    626         if isinstance(state, dict):

AttributeError: 'list' object has no attribute 'get'

I investigated more and i fixed this previous commit
2f9c3a3

I extended the previous check with 'fromImage' in self.request.url, so to restrict that check which
refers to install_image and only. Because self.headers.get('transfer-encoding') == 'chunked' is valid in other cases too. This way everything seems to work fine!

done

Checklist (tick everything that applies)

• Code linting (required, can be done after the PR checks)
• Tests

[coveralls]

Changes Unknown when pulling 467293a on johnnyWalnut:fix_docker_list_containers into ** on apache:trunk**.

[tonybaloney]

👍

[tonybaloney]

thanks for your contribution! merged.