Free plugin identifier on cleanup.

src/mosquitto_broker_internal.h

@@ -178,6 +178,7 @@ struct mosquitto__auth_plugin{
 	void *lib;
 	void *user_data;
 	int (*plugin_version)(void);
+	struct mosquitto_plugin_id_t *identifier;
 
 	FUNC_plugin_init_v5 plugin_init_v5;
 	FUNC_plugin_cleanup_v5 plugin_cleanup_v5;

src/plugin.c

@@ -86,6 +86,7 @@ int plugin__load_v5(struct mosquitto__listener *listener, struct mosquitto__auth
 
 	plugin->lib = lib;
 	plugin->user_data = NULL;
+	plugin->identifier = pid;
 
 	if(plugin->plugin_init_v5){
 		rc = plugin->plugin_init_v5(pid, &plugin->user_data, options, option_count);

src/security.c

@@ -406,6 +406,8 @@ static void security__module_cleanup_single(struct mosquitto__security_options *
 					opts->auth_plugin_configs[i].plugin.user_data,
 					opts->auth_plugin_configs[i].options,
 					opts->auth_plugin_configs[i].option_count);
+			mosquitto__free(opts->auth_plugin_configs[i].plugin.identifier);
+			opts->auth_plugin_configs[i].plugin.identifier = NULL;
 
 		}else if(opts->auth_plugin_configs[i].plugin.version == 4){
 			opts->auth_plugin_configs[i].plugin.plugin_cleanup_v4(