Add host argument to s3_connect.  Update unit test patches to match.
Host argument is now required by boto.  Latest version of boto provides a
hook to read from a .boto file, and there is a way for remote-task
to set such a file up and then read from it.  However, it's not
clear how to get the .boto file to the task instances in a multi-instance
cluster so that the file would be read by boto when reducers open
their own streams to output to an S3 file.