cyclades: Use vm.flavor_id instead of vm.flavor.id

Get the ID of the flavor of the VM without getting the flavor object
from DB.

Changelog

@@ -33,6 +33,7 @@ Cyclades
 
 * Fix a few occurrences of HTTP 500 errors being triggered due to insufficient
  validation of incoming requests in the Network API
+* Speed up some API calls by fixing the relevant DB queries
 
 .. _Changelog-0.15rc4:
 

snf-cyclades-app/synnefo/api/servers.py

@@ -178,8 +178,8 @@ def vm_to_dict(vm, detail=False):
         d['hostId'] = vm.hostid
         d['updated'] = utils.isoformat(vm.updated)
         d['created'] = utils.isoformat(vm.created)
-        d['flavor'] = {"id": vm.flavor.id,
-                       "links": util.flavor_to_links(vm.flavor.id)}
+        d['flavor'] = {"id": vm.flavor_id,
+                       "links": util.flavor_to_links(vm.flavor_id)}
         d['image'] = {"id": vm.imageid,
                       "links": util.image_to_links(vm.imageid)}
         d['suspended'] = vm.suspended