qt: Prevent thread/memory leak on exiting RPCConsole

Make ownership of the QThread object clear, so that the RPCConsole
can wait for the executor thread to quit before shutdown is called. This
increases overall thread safety, and prevents some objects from leaking
on exit.

src/qt/bitcoin.cpp

@@ -409,6 +409,11 @@ void BitcoinApplication::requestInitialize()
 
 void BitcoinApplication::requestShutdown()
 {
+    // Show a simple window indicating shutdown status
+    // Do this first as some of the steps may take some time below,
+    // for example the RPC console may still be executing a command.
+    ShutdownWindow::showShutdownWindow(window);
+
     qDebug() << __func__ << ": Requesting shutdown";
     startThread();
     window->hide();
@@ -423,9 +428,6 @@ void BitcoinApplication::requestShutdown()
     delete clientModel;
     clientModel = 0;
 
-    // Show a simple window indicating shutdown status
-    ShutdownWindow::showShutdownWindow(window);
-
     // Request shutdown from core thread
     Q_EMIT requestedShutdown();
 }