engine: Change OpenStack SDK version

Subnet creation code updated to use the non-deprecated entities.
Also marking subnet explicitly as DHCP to make sure it will be used.

Change-Id: I148e6efa3edc9adbae52778fd8e1aed34e03da90
Related-To: https://bugzilla.redhat.com/1064749
Signed-off-by: Mike Kolesnik <mkolesni@redhat.com>