[MERGE] Fix bzr failing to stack when a server requests it and the branch it is pushing from cannot stack but the branch it should stack on can.

[Bundle Buggy]

Bundle Buggy has detected this merge request.

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C1237435799.15722.199.camel%40lifeless-64%3E
Project: Bazaar