Attempted to fix bug regarding the convar "sv_shakeflyby_turnoffinvehicle"

Added server convar "sv_shakeflyby_turnoffinvehicle" which changes whether the effect will occur in vehicles for every client on the server

Requested by Virgiliu314

Fixed the shake occuring in vehicle while driving (thanks Fractal-Eternal !)

Added convar "shakeflyby_turnoffinvehicle" for vehicle mods that use different methods to create vehicles.