pborman/uuid and google/uuid used to be different versions of
the same package, but now pborman/uuid is a compatibility wrapper
around google/uuid, maintained by the same person.
Clean up some of the usage as the functions differ slightly.
Not yet removed some uses of pborman/uuid in vendored code but
I have PRs in process for these.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
