lok: joinThreads - take down configmgr's write-thread.

Change-Id: I1f9b6b88ef7e97da02fecf2035f953584cd28c16
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/170674
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>

desktop/source/lib/init.cxx

@@ -106,6 +106,8 @@
 #include <com/sun/star/lang/XMultiServiceFactory.hpp>
 #include <com/sun/star/style/XStyleFamiliesSupplier.hpp>
 #include <com/sun/star/util/URLTransformer.hpp>
+#include <com/sun/star/util/XFlushable.hpp>
+#include <com/sun/star/configuration/theDefaultProvider.hpp>
 #include <com/sun/star/datatransfer/clipboard/XClipboard.hpp>
 #include <com/sun/star/datatransfer/UnsupportedFlavorException.hpp>
 #include <com/sun/star/datatransfer/XTransferable2.hpp>
@@ -3441,6 +3443,12 @@ static int lo_joinThreads(LibreOfficeKit* /* pThis */)
     if (joinable && !joinable->joinThreads())
         return 0;
 
+    // Ensure configmgr's write thread is down
+    css::uno::Reference< css::util::XFlushable >(
+        css::configuration::theDefaultProvider::get(
+            comphelper::getProcessComponentContext()),
+        css::uno::UNO_QUERY_THROW)->flush();
+
     return 1;
 }