Failure looks like:

```
Entering test case "ComputeTimeSmart"
test_bitcoin: sync.cpp:100: void potential_deadlock_detected(const std::pair<void*, void*>&, const LockStack&, const LockStack&): Assertion `false' failed.
unknown location(0): fatal error in "ComputeTimeSmart": signal: SIGABRT (application abort requested)
wallet/test/wallet_tests.cpp(566): last checkpoint
```

Reproducible with:

```
./configure --enable-debug
make -C src test/test_bitcoin && src/test/test_bitcoin --log_level=test_suite --run_test=wallet_tests/ComputeTimeSmart
```

Seems to be caused by acquiring `cs_main` inside `CWallet::ComputeTimeSmart` in #11041.

I think this may be causing timeouts on travis like: https://travis-ci.org/bitcoin/bitcoin/jobs/353005676#L2692