Modify action_factory to store actions in DB

 * Action factory register actions in DB at starting
 * Added script tools/sync_db.sh for sync with db
   (Updates system actions, it is required before
   first Mistral launch)
 * Changed init Mistral in devstack: we must do
   sync_db before the launching.

 * Since we have to write all actions in DB, unit
   test are also modified:
    * Now in tearDown() we don't drop db at all,
      but just delete all things except Actions.
    * Created heavy_init() method as a replacement
      setUpClass(), see comments in tests/base.py
    * Register actions operation is too much expensive
      operation so we create db and init actions in
      heavy_init() method.

TODO:
 * Provide executor info to construct action class in
   runtime using action_factory
 * Modify/write an instruction 'How to start Mistral'

Change-Id: If4416c4da5c05189126c109aa613a0303c1b7ef0