MINOR: hlua: properly handle hlua_process_task HLUA_E_ETMOUT

In hlua_process_task: when HLUA_E_ETMOUT was returned by
hlua_ctx_resume(), meaning that the lua task reached
tune.lua.task-timeout (default: none),
we logged "Lua task: unknown error." before stopping the task.

Now we properly handle HLUA_E_ETMOUT to report a meaningful error
message.
diff --git a/src/hlua.c b/src/hlua.c
index 263d254..2ea15b9 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -8576,16 +8576,16 @@
 		break;
 
 	/* finished with error. */
+	case HLUA_E_ETMOUT:
+		SEND_ERR(NULL, "Lua task: execution timeout.\n");
+		goto err_task_abort;
 	case HLUA_E_ERRMSG:
 		SEND_ERR(NULL, "Lua task: %s.\n", lua_tostring(hlua->T, -1));
-		hlua_ctx_destroy(hlua);
-		task_destroy(task);
-		task = NULL;
-		break;
-
+		goto err_task_abort;
 	case HLUA_E_ERR:
 	default:
 		SEND_ERR(NULL, "Lua task: unknown error.\n");
+	err_task_abort:
 		hlua_ctx_destroy(hlua);
 		task_destroy(task);
 		task = NULL;