This implements the new Put() operation such that
Get()/Put() maintains a refcount for each ID, mounting
only on first Get() and unmounting on the last Get().
This means we avoid littering the system with lots of mounts
and free resources related to them.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Upstream-commit: 5fe26ee426b9d748605c538829f30885462ad932
Component: engine
bb99a3bd7b