Migrate logic from NewUUID function into the pvRenamer function.
PR #2133 switched to a new NewUUID function that returns an error, but
the invocation of that function needs to happen within the pvRenamer
closure. Because the new function returns an error, the pvRenamer should
return the error, the signature needs to be changed and the return
checked.
Signed-off-by: John Naulty <johnnaulty@bitgo.com>
cd860771c2