ganeti-noded: Fix bug when export didn't succeed for all disks

snap_disks can contain boolean values. They weren't handled correctly.
The error message was “Error while executing backend function: Invalid
object passed to FromDict: expected dict, got <type 'bool'>”.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

daemons/ganeti-noded

@@ -355,8 +355,14 @@ class NodeHttpServer(http.server.HttpServer):
 
     """
     instance = objects.Instance.FromDict(params[0])
-    snap_disks = [objects.Disk.FromDict(str_data)
-                  for str_data in params[1]]
+
+    snap_disks = []
+    for disk in params[1]:
+      if isinstance(disk, bool):
+        snap_disks.append(disk)
+      else:
+        snap_disks.append(objects.Disk.FromDict(disk))
+
     return backend.FinalizeExport(instance, snap_disks)
 
   @staticmethod