backend: Fix extra_query of smart_search_asn

Add code for passing an extra_query to the smart_search_asn internal backend
function.

Fixes #911

nipap/nipap/xmlrpc.py

@@ -868,7 +868,9 @@ def smart_search_asn(self, args):
         """
 
         try:
-            return self.nip.smart_search_asn(args.get('auth'), args.get('query_string'), args.get('search_options') or {})
+            return self.nip.smart_search_asn(args.get('auth'),
+                args.get('query_string'), args.get('search_options') or {},
+                args.get('extra_query'))
         except (AuthError, NipapError) as exc:
             raise Fault(exc.error_code, str(exc))