Fix bug: deployable object related bugs.
Fix bug: deployable object related bugs.

1. Change _get_parent_root_uuid to _get_parent_root_id and root_uuid
to root_id.
2. Correct some spelling errors in the comments line.
3. Remove uuid check in the create function, because the db model
will create one automatically.

Change-Id: I6265a2a613d7e092a994fd007c56b9cc620d2c21

openstack/nomad