Allow graphdriver plugins to use v2

Currently the plugin initialization is too late for a loaded v2 plugin
to be usable as a graph driver.

This moves the initialization up before we create the graph driver.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>
(cherry picked from commit 020b051dfb)
Signed-off-by: Victor Vieux <victorvieux@gmail.com>

daemon/daemon.go

@@ -550,7 +550,12 @@ func NewDaemon(config *Config, registryService registry.Service, containerdRemot
 		driverName = config.GraphDriver
 	}
 
+	d.RegistryService = registryService
 	d.PluginStore = pluginstore.NewStore(config.Root)
+	// Plugin system initialization should happen before restore. Do not change order.
+	if err := d.pluginInit(config, containerdRemote); err != nil {
+		return nil, err
+	}
 
 	d.layerStore, err = layer.NewStoreFromOptions(layer.StoreOptions{
 		StorePath:                 config.Root,
@@ -649,7 +654,6 @@ func NewDaemon(config *Config, registryService registry.Service, containerdRemot
 		Type:   config.LogConfig.Type,
 		Config: config.LogConfig.Config,
 	}
-	d.RegistryService = registryService
 	d.EventsService = eventsService
 	d.volumes = volStore
 	d.root = config.Root
@@ -668,11 +672,6 @@ func NewDaemon(config *Config, registryService registry.Service, containerdRemot
 		return nil, err
 	}
 
-	// Plugin system initialization should happen before restore. Do not change order.
-	if err := d.pluginInit(config, containerdRemote); err != nil {
-		return nil, err
-	}
-
 	if err := d.restore(); err != nil {
 		return nil, err
 	}

daemon/graphdriver/plugin.go

@@ -3,6 +3,7 @@ package graphdriver
 import (
 	"fmt"
 	"io"
+	"path/filepath"
 
 	"github.com/docker/docker/pkg/plugingetter"
 )
@@ -26,5 +27,5 @@ func lookupPlugin(name, home string, opts []string, pg plugingetter.PluginGetter
 
 func newPluginDriver(name, home string, opts []string, c pluginClient) (Driver, error) {
 	proxy := &graphDriverProxy{name, c}
-	return proxy, proxy.Init(home, opts)
+	return proxy, proxy.Init(filepath.Join(home, name), opts)
 }