Fixes various issues with Backpack Watertanks / Defibs by slapping NODROP on them
Changes all watertanks and the defib to use the Atmos watertank equip method
Fixes a runtime that could happen if someone melted the Atmos watertank off of you
Merge pull request #6223 from Ergovisavi/back_slot_toggle_items_fixes

Fixing issues and updating equip method for Watertank Backpack / Defib