core: move reset_arguments() to the end of main's finish

core: move reset_arguments() to the end of main's finish

Fixes #16991

fb39af4ce42d7ef9af63009f271f404038703704 replaced `free_arguments()` with
`reset_arguments()`, which frees arg_* variables as before, but also resets all
of them to the default values. `reset_arguments()` was positioned
in such a way that it overrode some arg_* values still in use at shutdown.

To avoid further unintentional resets, I moved `reset_arguments()`
right before the return, when nothing else will be using the arg_* variables.