Make rsync quiet by default, with push --verbose for more info

`dotcloud push --rsync` presently uses `rsync -v` by default, and recently
added `--progress` as well.  These options aren't suitable for anything but
a tiny repository, especially when running the CLI over SSH. However it's
even more concerning that the verbosity of rsync potentially obscures error
messages by filling the screen with pointless output.

This commit changes rsync to use its default quiet behavior, with the
current behavior available using `dotcloud push --verbose`