Disk quota not enabled for isolate

[kyfuse]

Describe the bug
Disk quota is not enabled for isolate, only fsize is. That means that you could bypass the max file size limit by creating tons of small files, overloading the system.

To Reproduce

1. Write code that creates a whole bunch of small files
2. Submit it to JudgeLite
3. Make JudgeLite hang (if the target system doesn't have enough storage space)

Expected behavior
JudgeLite should not hang (ideally, disk quota should be enabled).

Additional context
This isn't too important of an issue to fix, since no one would do this by accident. Plus, who would even think to try this?
However, it's important enough to leave this note here, in case someone does know how to fix this. I don't remember why we disabled disk quota, but there's probably a reason. Oh well.