FilterConfigNode: existing properties not overwritten?!

According to the std::map::insert() documentation, it does not
overwrite existing values in the map. This is not what is intended
here, property values in the filter *should* supersede existing
values.

This was found when looking at the code and has not shown up
as a real failure yet?!

src/syncevo/FilterConfigNode.cpp

@@ -85,7 +85,8 @@ void FilterConfigNode::readProperties(map<string, string> &props) const
     m_readOnlyNode->readProperties(props);
 
     BOOST_FOREACH(const StringPair &filter, m_filter) {
-        props.insert(filter);
+        // overwrite existing values or add new ones
+        props[filter.first] = filter.second;
     }
 }