The docker volume ls -f dangling=true filter was
inverted; the filtered results actually returned all
non-dangling volumes.
This fixes the filter and adds some integration tests
to test the correct behavior.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Upstream-commit: 1cbf9047b3be1bee39a72e96808581ff3c312a6c
Component: engine
