Support wfs request urls with "&amp;" at the end

For WFS servers with urls like "http://localhost:8080/map/mapserv?map=/opt/data/carto/world.www.map&", the capabilities document might look like this:

```
...
<ows:Operation name="GetFeature">
  <ows:DCP>
    <ows:HTTP>
      <ows:Get xlink:type="simple" xlink:href="http://localhost:8080/map/mapserv?map=/opt/data/carto/world.www.map&amp;"/>     
      <ows:Post xlink:type="simple" xlink:href="http://localhost:8080/map/mapserv?map=/opt/data/carto/world.www.map&amp;"/>
    </ows:HTTP>
  </ows:DCP>
  ...
```

The "&" at the end of the url is a "&amp;amp;" in the capabilities, which is currently not handled properly.