[StarCluster] small but possibly expensive error

[Cedar McKay]

When following:
http://starcluster.readthedocs.org/en/latest/manual/create_new_ami.html

I had to append
--force-spot-master 
to get a single node to launch as a spot instance. This actually can add up to real money when configuring and frequently restarting an expensive instance.  The docs seem to imply that offering a bid '-b' is adequate, but it wasn't in my case. Updating the docs to reflect this would be appreciated!

thanks,
Cedar