test: silence TSAN false positive in coinstatsindex_initial_sync

Fixes https://github.com/bitcoin/bitcoin/issues/25365

src/test/coinstatsindex_tests.cpp

@@ -76,10 +76,16 @@ BOOST_FIXTURE_TEST_CASE(coinstatsindex_initial_sync, TestChain100Setup)
 
     BOOST_CHECK(block_index != new_block_index);
 
+    // It is not safe to stop and destroy the index until it finishes handling
+    // the last BlockConnected notification. The BlockUntilSyncedToCurrentChain()
+    // call above is sufficient to ensure this, but the
+    // SyncWithValidationInterfaceQueue() call below is also needed to ensure
+    // TSAN always sees the test thread waiting for the notification thread, and
+    // avoid potential false positive reports.
+    SyncWithValidationInterfaceQueue();
+
     // Shutdown sequence (c.f. Shutdown() in init.cpp)
     coin_stats_index.Stop();
-
-    // Rest of shutdown sequence and destructors happen in ~TestingSetup()
 }
 
 // Test shutdown between BlockConnected and ChainStateFlushed notifications,