Fix OS tweaks call

The feature was not getting properly triggered, move it as
first operation in the configure

Signed-off-by: Flavio Crisciani <flavio.crisciani@docker.com>

libnetwork/drivers/overlay/overlay.go

@@ -180,6 +180,10 @@ func Fini(drv driverapi.Driver) {
 }
 
 func (d *driver) configure() error {
+
+	// Apply OS specific kernel configs if needed
+	d.initOS.Do(applyOStweaks)
+
 	if d.store == nil {
 		return nil
 	}
@@ -188,9 +192,6 @@ func (d *driver) configure() error {
 		return d.initializeVxlanIdm()
 	}
 
-	// Apply OS specific kernel configs if needed
-	d.initOS.Do(applyOStweaks)
-
 	return nil
 }