Fix lua backend, which ignored first running entry

Summary: Before, lua backend was launched with worksheet loading and have time for parsing lua start information (Lua 5.2.4 Copyright (C) 1994-2015 Lua.org, PUC-Rio). But now, first command go to lua, before start information parsing and this leads, that output of this command erroneously be removed. So I add @asemke suggestion, that solve this problem.

Test Plan:

1. Run lua backend without patch and check, that first runned entry haven't output result.
2. Apply patch
3. Check, that now first runned entry have output result.

Reviewers: Cantor

Subscribers: asemke, Cantor, KDE Edu

Tags: KDE Edu, Cantor

Differential Revision: https://phabricator.kde.org/D11792