Change "service inspect" to show defaults in place of empty fields

This adds a new parameter insertDefaults to /services/{id}. When this is
set, an empty field (such as UpdateConfig) will be populated with
default values in the API response. Make "service inspect" use this, so
that empty fields do not result in missing information when inspecting a
service.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

command/system/inspect.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/cli"
 	"github.com/docker/docker/cli/command"
 	"github.com/docker/docker/cli/command/inspect"
@@ -79,7 +80,8 @@ func inspectNode(ctx context.Context, dockerCli *command.DockerCli) inspect.GetR
 
 func inspectService(ctx context.Context, dockerCli *command.DockerCli) inspect.GetRefFunc {
 	return func(ref string) (interface{}, []byte, error) {
-		return dockerCli.Client().ServiceInspectWithRaw(ctx, ref)
+		// Service inspect shows defaults values in empty fields.
+		return dockerCli.Client().ServiceInspectWithRaw(ctx, ref, types.ServiceInspectOptions{InsertDefaults: true})
 	}
 }