[MERGE] Remove a spurious call to 'get_master_branch()'

[Martin Pool]

Martin Pool has voted tweak.
Status is now: Conditionally approved
Comment:
Agree you should remove or explain the traceback.

+            mutter('hpss call:   %r', args)

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C46AA4DDC.6060204%40arbash-meinel.com%3E