Change plasma logout service call from "ksmserver" to "Shutdown"

[nickylivardo]

After the plasma 6 update, the autologout function no longer works anymore, the detail issue i've already explained here :
Askannz/optimus-manager#575

Anyway i've tested this commit and it works great and fixed the issue.

[Shatur]

I think we should try both, for Plasma 6 and 5. Just put the logic next to each other.

[nickylivardo]

hello i've updated the commit, this should work both for plasma 6 and 5 now.

[Shatur]

Please, split into two blocks, as other.

[Shatur]

Thank you!