Without this change and running:
```
cd stress
while cargo run -- --nr-threads=4 -i 1000 --verbose --busy-timeout=0; do; done
```
I can produce a deadlock quite reliably.
With this change, I can't.
Even with 5 second busy timeout (the default), the run makes progress
although it is slow as hell because of the busy timeout.
Full disclosure: i couldn't figure out based on parking lot RwLock
semantics why this would fix it, so maybe it just lessens the
probability
Reviewed-by: Preston Thorpe <preston@turso.tech>
Closes#3759
56e9ba9eae