Currently access to the Devices map is serialized by the main
DeviceSet lock, but we need to access it outside that lock, so we
add a separate lock for this and grab that everywhere we modify
or read the map.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Upstream-commit: 70826e8b3fee27b971852aad89053507c6866d3e
Component: engine
bd0bcefa7f