No packages installed after repeat modification of initial packages list in Fuel after node provisioning

[Andrey Lavrentyev]

Detailed bug description:
No packages installed after 2nd, 3rd, 4th, ... modification of initial packages list in Fuel after node provisioning.
It looks like it caches initial package list and use the cache (or prepared snapshot) for any further provisions.

Steps to reproduce:

1. Create env
2. Add 'tree' package to the initial packages list in Settings
3. Provision node
4. Add new node or delete provisioned node
5. Delete 'tree' package, and add a new package that is not in the list ('git' for example)
6. Provision the node
7. Check that there is no 'tree' package and there is 'git' package on the provisioned node

Expected results:
no 'tree' package and 'git' package is presented

Actual result:
'tree' package is presented, no 'git' package

Reproducibility:
every time

[root@nailgun ~]# shotgun2 short-report
cat /etc/fuel_build_id:
 427
cat /etc/fuel_build_number:
 427
cat /etc/fuel_release:
 9.0
cat /etc/fuel_openstack_version:
 mitaka-9.0
rpm -qa | egrep 'fuel|astute|network-checker|nailgun|packetary|shotgun':
 fuel-release-9.0.0-1.mos6347.noarch
 fuel-misc-9.0.0-1.mos8415.noarch
 fuel-bootstrap-cli-9.0.0-1.mos284.noarch
 fuel-migrate-9.0.0-1.mos8415.noarch
 rubygem-astute-9.0.0-1.mos747.noarch
 fuel-provisioning-scripts-9.0.0-1.mos8718.noarch
 network-checker-9.0.0-1.mos72.x86_64
 fuel-mirror-9.0.0-1.mos137.noarch
 fuel-openstack-metadata-9.0.0-1.mos8718.noarch
 fuel-notify-9.0.0-1.mos8415.noarch
 nailgun-mcagents-9.0.0-1.mos747.noarch
 python-fuelclient-9.0.0-1.mos319.noarch
 fuelmenu-9.0.0-1.mos270.noarch
 fuel-9.0.0-1.mos6347.noarch
 fuel-utils-9.0.0-1.mos8415.noarch
 fuel-setup-9.0.0-1.mos6347.noarch
 fuel-library9.0-9.0.0-1.mos8415.noarch
 shotgun-9.0.0-1.mos90.noarch
 fuel-agent-9.0.0-1.mos284.noarch
 fuel-ui-9.0.0-1.mos2710.noarch
 fuel-ostf-9.0.0-1.mos934.noarch
 python-packetary-9.0.0-1.mos137.noarch
 fuel-nailgun-9.0.0-1.mos8718.noarch