Pass down store configs to driver

- Renamed netlabel prefixes to accomodate both global
       and local store configs.
     - Added a `private` marker.
     - Skipping the data store configs for remote driver
       so that external plugins don't get it as there is
       no secure and sane way to coordinate providing
       data store access to external plugins.

Signed-off-by: Jana Radhakrishnan <mrjana@docker.com>

drivers/overlay/overlay.go

@@ -79,8 +79,8 @@ func (d *driver) configure() error {
 	}
 
 	d.once.Do(func() {
-		provider, provOk := d.config[netlabel.KVProvider]
-		provURL, urlOk := d.config[netlabel.KVProviderURL]
+		provider, provOk := d.config[netlabel.GlobalKVProvider]
+		provURL, urlOk := d.config[netlabel.GlobalKVProviderURL]
 
 		if provOk && urlOk {
 			cfg := &datastore.ScopeCfg{
@@ -89,7 +89,7 @@ func (d *driver) configure() error {
 					Address:  provURL.(string),
 				},
 			}
-			provConfig, confOk := d.config[netlabel.KVProviderConfig]
+			provConfig, confOk := d.config[netlabel.GlobalKVProviderConfig]
 			if confOk {
 				cfg.Client.Config = provConfig.(*store.Config)
 			}