Merge #15410: test: txindex: interrupt threadGroup before calling destructor

fab6b07c16 test: txindex: interrupt threadGroup before calling destructor (MarcoFalke)

Pull request description:

  Fixes the data races with the tread sanitizer such as

  * https://travis-ci.org/MarcoFalke/bitcoin/jobs/492330554
  * https://github.com/bitcoin/bitcoin/pull/15402#discussion_r256676622
  * ...

Tree-SHA512: 40608c70d92a1dd68efc1d41eecc8e2fb7738508e21f91f0ad353adcceed60fa624f15bf72a5b69a9444157b261183abbe9fc4cc5dd8aebc1c49506b239e8e88

src/test/txindex_tests.cpp

@@ -69,7 +69,13 @@ BOOST_FIXTURE_TEST_CASE(txindex_initial_sync, TestChain100Setup)
         }
     }
 
-    txindex.Stop(); // Stop thread before calling destructor
+    // shutdown sequence (c.f. Shutdown() in init.cpp)
+    txindex.Stop();
+
+    threadGroup.interrupt_all();
+    threadGroup.join_all();
+
+    // Rest of shutdown sequence and destructors happen in ~TestingSetup()
 }
 
 BOOST_AUTO_TEST_SUITE_END()