autotest: add test for plane-wind-failsafe.lua

[peterbarker]

Summary

Adds an autotest which thoroughly tests the Plane wind failsafe example.

Classification & Testing (check all that apply and add your own)

• Checked by a human programmer
• Non-functional change
• No-binary change
• Infrastructure change (e.g. unit tests, helper scripts)
• Automated test(s) verify changes (e.g. unit test, autotest)
• Tested manually, description below (e.g. SITL)
• Tested on hardware
• Logs attached
• Logs available on request

Description

Exhautsively tests this script in preparation for expansion.