commander: prevent setting nav_state to takeoff after disarming

[mahima-yoga]

Solved Problem

When auto-landing while the current nav_state is set to a takeoff mode, the nav_state after disarming reverts to takeoff. On the next arming, the vehicle immediately initiates takeoff

Solution

• Prevent _nav_state_after_disarming from being set to an auto-takeoff state by adding a check for takeoff modes.

Changelog Entry

For release notes:

Feature/Bugfix Prevent nav_state_after_disarming from being set to a takeoff mode.

Alternatives

Open to alternative solutions

Test coverage

• Tested in SITL:

NAVIGATION_STATE_POSCTL = 2   
NAVIGATION_STATE_AUTO_TAKEOFF = 17        
NAVIGATION_STATE_AUTO_LAND = 18  

[dakejahl]

Thanks for the fix!