Merged docker-utils and delta tests into a single test suite. They are
now ran as part of the integration tests using the real engine.
Change-type: patch
Now the tests are ran against the actual docker engine instead of
against mockerode.
The new tests actually caught a bug in
`volumeManager.removeOrphanedVolumes`, where that function would try to
remove volumes for stopped containers, causing an exception.
This commit also fixes that bug.
