Fixi caching in zsh completion (#5122)

I found several issues with zsh completion code:

1. typo in cache filename: "SYS_ALL_PROPRTIES", so cache just not loading from this file
2. cache stored in one file, despite user or system mode. So it can be loaded later in wrong mode
3. most serious problem: broken logic - it retrieves cache when _cache_invalid is true

How to reproduce: type "systemctl --user status <TAB>" and you will see user units. Then press
control+C and type "systemctl --system status <TAB>" in same session and you'll see user units again
(cherry picked from commit 88e4dbd5)