coverity#704085 Unchecked return value

other patterns aren't really the same as this one

Change-Id: Ie26fd5c01d156004f755017a859679e904a29520

ucb/source/ucp/ftp/ftpcontent.cxx

@@ -941,7 +941,7 @@ Sequence<Any> FTPContent::setPropertyValues(
     if(evt.getLength()) {
         // title has changed
         notifyPropertiesChange(evt);
-        exchange(new FTPContentIdentifier(m_aFTPURL.ident(false,false)));
+        (void)exchange(new FTPContentIdentifier(m_aFTPURL.ident(false,false)));
     }
 
     return ret;