Task: Modify AirdropApproach

[miyatakazuya]

Feature

Add logic to trigger variations of landing based on if it is on Airdrop 1 & 3, 2 & 4. Moreover:

• 1 & 3 will continue flying
• 2 & 4 triggers a switch to landing
  • 2 will enter a refuel loitering state
  • 4 will terminate the mission

[kimichenn]

#250