Check_MK Werk 7330: Fix confusions when working with localized shell environments

ID: 7330 Title: Fix confusions when working with localized shell environments Component: Site Management Level: 1 Class: Bug fix Version: 1.6.0i1 When switching to the site user context we now enforce a non localized environment. The reason for this configuration is that the parameters and outputs of the monitoring plug-ins are localized. If they are called from the core, they are always language-neutral. During manual testing, the plugins may behave differently depending on the localization of the user's environment variables. This can lead to confusion during tests.