forced saveConf does not correctly report success on MySQL/MariaDB

Affected version

Version: 2.16.2

Summary

• Try to run convertConfig from Files to MySQL

Unable to store configuration 1: Lemonldap::NG::Common::Conf::Backends::CDBI loaded.
Get configuration 1.
Configuration 1 stored.

(the process stops with an exit code of 7 and no other sessions are converted, despite success)

Another way to reproduce the issue

lemonldap-ng-cli -force 1 -yes 1 set https 1
cfgNum forced with 1Could not save configuration:

Possible fixes

In saveConf:

    return ( $self->unlock() ? $tmp : UNKNOWN_ERROR );

In MySQL the unlock function returns false if the lock hasn't been acquired first, which is the case when "force" has been set