slapos/proxy: use slapos API when forwarding request

Eventhough implementation might be a bit more efficient is we use the
low level API, we probably don't need performance here and it's easier
to use the request API

slapos/proxy/views.py

@@ -570,14 +570,21 @@ def forwardRequestToExternalMaster(master_url, request_form):
   new_request_form = request_form.copy()
   filter_kw = loads(new_request_form['filter_xml'].encode('utf-8'))
   filter_kw['source_instance_id'] = partition_reference
-  new_request_form['filter_xml'] = dumps(filter_kw)
 
-  xml = slap._connection_helper.POST('/requestComputerPartition', data=new_request_form)
-  partition = loads(xml)
+  partition = slap.registerOpenOrder().request(
+      software_release=request_form['software_release'],
+      partition_reference=request_form['partition_reference'],
+      partition_parameter_kw=loads(request_form['partition_parameter_xml'].encode('utf-8')),
+      software_type=request_form.get('software_type', ''),
+      filter_kw=filter_kw,
+      state=loads(request_form['state'].encode('utf-8')),
+      shared=loads(request_form['shared_xml'].encode('utf-8')),
+  )
 
   # XXX move to other end
-  partition._master_url = master_url
-
+  partition._master_url = master_url # type: ignore
+  partition._connection_helper = None
+  partition._software_release_document = request_form['software_release'] # type: ignore
   return dumps(partition)
 
 def getAllocatedInstance(partition_reference):

slapos/tests/test_slapproxy.py

@@ -1574,6 +1574,12 @@ database_uri = %(tempdir)s/lib/external_proxy.db
 
     self._checkInstanceIsFowarded(instance_reference, dummy_parameter_dict, self.external_software_release)
 
+    instance_parameter_dict = partition.getInstanceParameterDict()
+    instance_parameter_dict.pop('timestamp')
+    self.assertEqual(dummy_parameter_dict, instance_parameter_dict)
+    self.assertEqual(self.external_software_release, partition.getSoftwareRelease())
+    self.assertEqual({}, partition.getConnectionParameterDict())
+
   def testRequestToCurrentMaster(self):
     """
     Explicitely ask deployment of an instance to current master