Object storage

don't merge before https://github.com/owncloud/3rdparty/pull/99 is in 3rdparty
- [ ] https://github.com/owncloud/3rdparty/pull/99 moves rackspace to 3rdparty, but files_external also provides it, causing tests to fail ...
- [x] swift test should create a new container on every test run and delete it afterwards
You can't :wink: 
If you do, the next test won't re-init the base hooks properly.
This is something that needs to be looked into at some point.