MM-12356 Add cli command "command delete" (#9553)

* Add cli command for deleting commands

* Add code/test for delete command

* Fix test

* Add confirm flag

* Update as per comments

* Uncomment test

* Fix test

app/command.go

@@ -423,10 +423,9 @@ func (a *App) DeleteCommand(commandId string) *model.AppError {
 	if !*a.Config().ServiceSettings.EnableCommands {
 		return model.NewAppError("DeleteCommand", "api.command.disabled.app_error", nil, "", http.StatusNotImplemented)
 	}
-
-	if err := (<-a.Srv.Store.Command().Delete(commandId, model.GetMillis())).Err; err != nil {
-		return err
+	result := <-a.Srv.Store.Command().Delete(commandId, model.GetMillis())
+	if result.Err != nil {
+		return result.Err
 	}
-
 	return nil
 }