NO_UNLOAD containers cannot be unloaded, even if liquid

[RenechCDDA]

Summary

Bugfixes "Containers with NO_UNLOAD cannot unload liquids"

Purpose of change

You could do things like dump pressurized liquid ammonia on the ground. This shouldn't be possible, and that's why NO_DROP exists - but while looking up WHY it was happening, I learned that liquids can always be removed from NO_UNLOAD containers.

Describe the solution

Don't return a check saying you can unload if there's a no unload flag! The flag check needs to be in the first return otherwise it short-circuits before it gets to checking for the flag.

Describe alternatives you've considered

I considered changing the order of the logic so no unload is always checked first, but I tried this solution first and it worked during testing, so...

Testing

Compiled locally and confirmed that this change prevented liquid ammonia from being removed from its pressure tank container. I also crafted with it and (after applying the fix for #59539) confirmed that crafting interactions worked as intended. I did not test with any other liquids.

Additional context

Ammonia was just a useful test item - it needs other PRs to address its ability to migrate outside of pressurized containers.

This changes some pretty old game logic so I won't be surprised if it breaks something. This definitely needs to pass all automated tests before merging, if nothing else.

There may be a much smarter way to code this. My C++ is still novice, at best.