Add some unit tests to the node and swarm cli code

Start work on adding unit tests to our cli code in order to have to
write less costly integration test.

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

command/node/remove.go

@@ -16,7 +16,7 @@ type removeOptions struct {
 	force bool
 }
 
-func newRemoveCommand(dockerCli *command.DockerCli) *cobra.Command {
+func newRemoveCommand(dockerCli command.Cli) *cobra.Command {
 	opts := removeOptions{}
 
 	cmd := &cobra.Command{
@@ -33,7 +33,7 @@ func newRemoveCommand(dockerCli *command.DockerCli) *cobra.Command {
 	return cmd
 }
 
-func runRemove(dockerCli *command.DockerCli, args []string, opts removeOptions) error {
+func runRemove(dockerCli command.Cli, args []string, opts removeOptions) error {
 	client := dockerCli.Client()
 	ctx := context.Background()