Copter: SmartRTL should give roll/pitch control back to pilot earlier while landing

[rmackay9]

SmartRTL (released with Copter-3.6) returns along the path the vehicle flew until it reaches home.

SmartRTL will return roll-pitch control to the pilot once the vehicle has reached the end of the return path. It may be however that the final point on the path is very very close to home (within 2m or so) meaning the pilot really doesn't regain control of the vehicle until the very last moment.

It would be good to check that we don't unnecessarily make points very close to home during takeoff and/or find another way to return roll/pitch control to the pilot when the vehicle is more like 10m from home.