QA for allocator in recreate-disks

QA for recreate-disks called it twice with a list of node; the first call
now uses an allocator.

Signed-off-by: Adam Ingrassia <api@google.com>
Signed-off-by: Bernardo Dal Seno <bdalseno@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>