misc/emacs: Fix a failure when /tmp/<file>.go exists.
misc/emacs: Fix a failure when /tmp/<file>.go exists.

R=sameer
CC=golang-dev
http://codereview.appspot.com/6296060

Committer: Sameer Ajmani <da4a4efb907a17fabb3e092841511e7f24e226cf@golang.org>

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang