Change mount-types to lowercase

these values were changed to lowercase in
https://github.com/docker/engine-api/commit/690cb2d08cfcca31cd02e68b23915b75386beecd,
but not changed accordingly in docker/docker.

this changes the mounttypes to lowercase

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Upstream-commit: 8f93128cd619e1d11be1bc0ae21f1362b1e3f9ad
Component: engine

components/engine/volume/volume.go

@@ -143,12 +143,12 @@ func (m *MountPoint) Path() string {
 // Type returns the type of mount point
 func (m *MountPoint) Type() string {
 	if m.Name != "" {
-		return "VOLUME"
+		return "volume"
 	}
 	if m.Source != "" {
-		return "BIND"
+		return "bind"
 	}
-	return "EPHEMERAL"
+	return "ephemeral"
 }
 
 // ParseVolumesFrom ensures that the supplied volumes-from is valid.