UG Edits: Migrate Instances, Conf Drive

- Edits to the Migrate Instances and Conf Drive sections of the CLI chapter
- Patch split from https://review.openstack.org/#/c/89581/

Change-Id: I7fef7f8e03aa1aa7362326169c961eb977d8d5c0
Imported Translations from Transifex

Change-Id: I6476dee8a12226b9ffbb7ac19134dd0b02ed7ada
Merge "UG Edits: Migrate Instances, Conf Drive"