Major changes:

 * decoupling the hooks/manager.py file from the charm.  It is now a
   script that is called from hooks/keystone_utils.py as it has to use
   the same Python version/libraries as the installed keystone payload
   software.  keystone_utils.py and manager.py communicate via a Unix
   Domain Socket using json, encoded to base64.
 * As Python3 requires absolute imports, the charmhelpers symlink has
   been removed from hooks, and the hooks and charmhelpers symlinks have
   been removed from the actions directory.  Instead, the path is
   adjusted so that the modules can be found.

Change-Id: I18996e15d2d08b1dacf0533132eae880cbb9aa32