Fixed extraction of facet_queries

The `facet_queries` XML element of Solr's response looks something like this: 

```
<lst name="facet_queries">
  <int name="price:[* TO 500]">2</int>
  <int name="price:[500 TO *]">1</int>
 </lst>
```
It doesn't have a nested `lst` tag, so I've replaced it with `node.child`

Cheers!
Tulio