labs: update apt pre-download for nova compute
labs: update apt pre-download for nova compute

Two packages are no longer necessary, one has been added for Juno.

Change-Id: I3ad3b360c05df26c60c4f9c4b42299d64615618e

openstack/training-labs,openstack/training-labs,dguitarbite/OpenStack-Labs,dguitarbite/OpenStack-Labs,openstack/training-labs,dguitarbite/OpenStack-Labs