Revise swarm init/update flags, add unlocking capability

- Neither swarm init or swarm update should take an unlock key
- Add an autolock flag to turn on autolock
- Make the necessary docker api changes
- Add SwarmGetUnlockKey API call and use it when turning on autolock
- Add swarm unlock-key subcommand

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

interface.go

@@ -119,6 +119,7 @@ type ServiceAPIClient interface {
 type SwarmAPIClient interface {
 	SwarmInit(ctx context.Context, req swarm.InitRequest) (string, error)
 	SwarmJoin(ctx context.Context, req swarm.JoinRequest) error
+	SwarmGetUnlockKey(ctx context.Context) (types.SwarmUnlockKeyResponse, error)
 	SwarmUnlock(ctx context.Context, req swarm.UnlockRequest) error
 	SwarmLeave(ctx context.Context, force bool) error
 	SwarmInspect(ctx context.Context) (swarm.Swarm, error)

swarm_get_unlock_key.go

@@ -0,0 +1,21 @@
+package client
+
+import (
+	"encoding/json"
+
+	"github.com/docker/docker/api/types"
+	"golang.org/x/net/context"
+)
+
+// SwarmGetUnlockKey retrieves the swarm's unlock key.
+func (cli *Client) SwarmGetUnlockKey(ctx context.Context) (types.SwarmUnlockKeyResponse, error) {
+	serverResp, err := cli.get(ctx, "/swarm/unlockkey", nil, nil)
+	if err != nil {
+		return types.SwarmUnlockKeyResponse{}, err
+	}
+
+	var response types.SwarmUnlockKeyResponse
+	err = json.NewDecoder(serverResp.body).Decode(&response)
+	ensureReaderClosed(serverResp)
+	return response, err
+}