[CI] Problems with `dispatch_job.py`

[boomanaiden154]

We're seeing some failure modes related to the job dispatching:

1. https://lab.llvm.org/staging/#/builders/192/builds/1314/steps/4/logs/stdio
2. https://lab.llvm.org/staging/#/builders/192/builds/1205/steps/4/logs/stdio
3. https://lab.llvm.org/staging/#/builders/192/builds/1317/steps/4/logs/stdio

These need to be fixed.