Fix bin scripts fo Python 3.

Fixes S3/Glacier and EC2 scripts so that they are valid Python 3. Some things
may still not work, but the scripts are now capable of running under Python 3.
This mostly involved updates to `print` statements.

Fixes the issue brought up in #2490 about `glacier`.

No tests, but I ran each manually in Python 2 and 3.

cc @jamesls, @kyleknap
I usually see this as sys.exit().  Any reason to use raise SystemExit?