fix: prevent getting jobs when generation running

[MaikoTan]

Description

fix #89

Type of changes

• Bugfix

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[Maeyanie]

I tested this and it appears to deadlock the instance when a poll happens. I'm guessing that's not a reentrant lock?

Testing on Win10, Python 3.10.8 from conda-forge.

Edit: Yeah, looking at the code, that lock is also acquired inside handle_request, which is inside that. Removing all 4 locks from handle_request (Which looks like they're unnecessary now that it's locked before calling that function? I don't know your code so not sure if it's called anywhere else.) seems to have fixed it.