Alas the valves are NOT part of the water heater and thus can be anwhere. However ther are a few prime suspects.
First. get access to the back side of the water heater (The inside of the motor home) usually there is a panel or something, often easily removed (As in no tools required) and the valves may well be there..... If you ever need to replace the electric heat element, it's there too.
Another place is the compartment NEXT to the water heater. or below it. depending on the design of your RV.
Beyond that it's trace the dang pipes time.
Home is where I park it!