Fix simAddVehicle for Car vehicle

[rajat2004]

Fixes: #

About

simAddVehicle API failed with Car with the error in #4109 (comment)
This PR fixes the extra reset call, allowing it to work for Car, CV vehicles

Alos update the docs for this API

How Has This Been Tested?

Using the script added in the PR -

airsim_runtime_car.mp4

For CV mode -

>>> import airsim
>>> cl = airsim.VehicleClient()
>>> cl.confirmConnection()
Connected!
Client Ver:1 (Min Req: 1), Server Ver:1 (Min Req: 1)

>>> pose = airsim.Pose()
>>> print(cl.simAddVehicle("CV2", "ComputerVision", pose))
True

Verified that HelloSpawnedDrones was working as expected

Screenshots (if appropriate):

Docs -

[zimmy87]

Tested this locally and it works for me, so I am moving ahead with merging; thanks for the contribution @rajat2004!