Migrate AccountGroup owner Id to UUID

Only internal groups have an Id and future support for external groups
will only have a UUID. This change is needed because existing LDAP
groups have an Id and may be the owner of an internal group. In order to
ease the future migration, allow internal groups to be owned by a UUID.

Change-Id: I126e79667e17b2113007c1c300f5f40c0bb4f9c0
11 files changed