showdebug vehicle auto-completion missing in the console

Hello,

As said in the title, there is not auto-completion entry for the vehicle in the showdebug section. If you could do this it would help people like me who are searching hours to setup vehicles.

Thanks by advance.

Added the console command as requested, see https://github.com/EpicGames/UnrealEngine/pull/4533 for the code changes.