create generic backend to cut dependency on daemon

 - create a volume-specific interface that for the methods of daemon
   that are used
 - remove dependency on daemon package by volume package of server
 - like 5087977fc1a4279be55f25e0b8782c9cf9bc65f3

Signed-off-by: Morgan Bauer <mbauer@us.ibm.com>

api/server/router/volume/backend.go

@@ -0,0 +1,16 @@
+package volume
+
+import (
+	// TODO return types need to be refactored into pkg
+	"github.com/docker/docker/api/types"
+)
+
+// Backend is the methods that need to be implemented to provide
+// volume specific functionality
+type Backend interface {
+	Volumes(filter string) ([]*types.Volume, error)
+	VolumeInspect(name string) (*types.Volume, error)
+	VolumeCreate(name, driverName string,
+		opts map[string]string) (*types.Volume, error)
+	VolumeRm(name string) error
+}

api/server/router/volume/volume.go

@@ -3,19 +3,18 @@ package volume
 import (
 	"github.com/docker/docker/api/server/router"
 	"github.com/docker/docker/api/server/router/local"
-	"github.com/docker/docker/daemon"
 )
 
 // volumesRouter is a router to talk with the volumes controller
 type volumeRouter struct {
-	daemon *daemon.Daemon
-	routes []router.Route
+	backend Backend
+	routes  []router.Route
 }
 
 // NewRouter initializes a new volumes router
-func NewRouter(d *daemon.Daemon) router.Router {
+func NewRouter(b Backend) router.Router {
 	r := &volumeRouter{
-		daemon: d,
+		backend: b,
 	}
 	r.initRoutes()
 	return r

api/server/router/volume/volume_routes.go

@@ -14,7 +14,7 @@ func (v *volumeRouter) getVolumesList(ctx context.Context, w http.ResponseWriter
 		return err
 	}
 
-	volumes, err := v.daemon.Volumes(r.Form.Get("filters"))
+	volumes, err := v.backend.Volumes(r.Form.Get("filters"))
 	if err != nil {
 		return err
 	}
@@ -26,7 +26,7 @@ func (v *volumeRouter) getVolumeByName(ctx context.Context, w http.ResponseWrite
 		return err
 	}
 
-	volume, err := v.daemon.VolumeInspect(vars["name"])
+	volume, err := v.backend.VolumeInspect(vars["name"])
 	if err != nil {
 		return err
 	}
@@ -47,7 +47,7 @@ func (v *volumeRouter) postVolumesCreate(ctx context.Context, w http.ResponseWri
 		return err
 	}
 
-	volume, err := v.daemon.VolumeCreate(req.Name, req.Driver, req.DriverOpts)
+	volume, err := v.backend.VolumeCreate(req.Name, req.Driver, req.DriverOpts)
 	if err != nil {
 		return err
 	}
@@ -58,7 +58,7 @@ func (v *volumeRouter) deleteVolumes(ctx context.Context, w http.ResponseWriter,
 	if err := httputils.ParseForm(r); err != nil {
 		return err
 	}
-	if err := v.daemon.VolumeRm(vars["name"]); err != nil {
+	if err := v.backend.VolumeRm(vars["name"]); err != nil {
 		return err
 	}
 	w.WriteHeader(http.StatusNoContent)