This makes all users of Put() have a corresponding call
to Get() which means we will be able to track whether
any particular ID is in use and if not unmount it.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Upstream-commit: bcaf6c2359d83acd5da54f499e21f4a148f491c5
Component: engine