Fixes for setup.py to work properly with PyPi.

* Include CHECKSUM in MANIFEST.in file.
* Update boto hash in submodule and setup.py.
* Update boto version string to 2.9.0-dev.
* Override setuptools sdist command in addition to build_py command because it's
  used when uploading to PyPi.
* Look for mock_storage_service.py in an additional place so it works when
  running from PyPi built source distribution.