Properly check HRESULT

Although the IEnumFORMATETC::Next documentation only mentions S_OK and
S_FALSE, there are error codes that also may be returned: e.g.,
0x800706BA RPC server unavailable (encountered locally in a unit test).
In that case, this used to loop infinitely.

We are only interested in S_OK result, so check for it.

Change-Id: I062e409e84efb68353321f7c48d922ec83191f73
Reviewed-on: https://gerrit.libreoffice.org/61621
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

dtrans/source/win32/dtobj/DOTransferable.cxx

@@ -281,7 +281,7 @@ void CDOTransferable::initFlavorList( )
         pEnumFormatEtc->Reset( );
 
         FORMATETC fetc;
-        while ( S_FALSE != pEnumFormatEtc->Next( 1, &fetc, nullptr ) )
+        while ( S_OK == pEnumFormatEtc->Next( 1, &fetc, nullptr ) )
         {
             // we use locales only to determine the
             // charset if there is text on the cliboard