engine: Add instance ID to MAC pool manager

When logging, it would be beneficial to know the instance ID of the
manager in order to identify on which objects the MAC addresses pool is
managed.

Change-Id: I46663116b60d083af7eb1334cc253834cb558a6c
Related-to: https://bugzilla.redhat.com/987825
Signed-off-by: Mike Kolesnik <mkolesni@redhat.com>