```
This PR fixes an early relocking race condition from #18811 where old
relock callback runs after new wallet unlock code and nRelockTime update
but before rpcRunLater call, causing early relock and incorrect
nRelockTime time
```
Backport of core PR18814.
Fix spurious wallet_descriptor.py failure like
https://build.bitcoinabc.org/viewLog.html?tab=buildLog&logTab=tree&filter=debug&expand=all&buildId=167449&_focus=3291&guest=1.