multinode ubuntu 1.7.0 to 1.7.1 upgrade doens't load old config

1) install 1.7.0 on 2 nodes
2) cluster the nodes
3) add some data to the cluster
4) run upgrade on both nodes

note: single/unclustered node upgrade works fine

root@domU-12-31-39-0A-35-B7:~# dpkg -i membase-server-enterprise_x86_1.7.1r-62-g1926675.deb
(Reading database ... 30889 files and directories currently installed.)
Preparing to replace membase-server 1.7.0 (using membase-server-enterprise_x86_1.7.1r-62-g1926675.deb) ...
 * Stopped Membase server
Upgrading previous membase ... (1.7.0)
Stopping previous membase ... (1.7.0)
 * Stopped Membase server
Saving previous membase config.dat ...
Cleaning symlinks ...
Unpacking replacement membase-server ...
Setting up membase-server (1.7.1r) ...
Upgrading from 1.7.0, directory /opt/membase/var/lib/membase/config ...
  /opt/membase/bin/mbupgrade -c /opt/membase/var/lib/membase/config -a yes
Automatic mode: running without interactive questions or confirmations.
Upgrading your Membase Server to 1.7.1r-62-g1926675.
The upgrade process might take awhile.
Analysing...
Previous config.dat file is /opt/membase/var/lib/membase/config/config.dat.debsave
Target node: ns_1@127.0.0.1
Done: previous node configuration is empty.
 * Started membase-server

You have successfully installed Membase Server.
Please browse to http://domU-12-31-39-0A-35-B7:8091/ to configure your server.
Please refer to http://couchbase.com for additional resources.

Please note that you have to update your firewall configuration to
allow connections to the following ports: 11211, 11210, 4369, 8091
and from 21100 to 21299.

By using this software you agree to the End User License Agreement.
See /opt/membase/LICENSE.txt.