Updating icinga cause the service user config to be reset on Windows

[P6g9YHK6]

seen on multiple windows version. we use the local system as the default user for most devices as it has the permissions required for our checks and when running an update for incinga2 on every devices the config for the service user is lost.

https://github.com/Icinga/icinga-powershell-framework/blob/b35f0a77b9ad423b660c2c9ef0f3df70398958a2/lib/core/icingaagent/setters/Set-IcingaAgentServiceUser.psm1#L49

the command to change the user only use "sc.exe" to change the user and it seems that the installer is ignoring previous config and resetting it anyway,

(we use the chocolatey package but i don't think it is linked.)

not sure to what repo this issue should be opened in but i didn't found any code for the installer and this issue is more linked to the installer interacting with previous configs than the PS framework

probably linked: https://github.com/Icinga/icinga-powershell-framework/issues/761

Expected Behavior: The installer should respect the existing service user configuration