[systest]Test 'repeatable_image_based' hangs on powering off slave node via SSH

[Artem Panchenko]

System test 'repeatable_image_based' hangs on step #4 while shutting down bootstrapped slave nodes:

2015-12-04 23:57:11,280 - INFO fuel_web_client.py:1626 -- Shutting down (warm) nodes [u'slave-01', u'slave-02', u'slave-03', u'slave-04', u'slave-05']
Build timed out (after 480 minutes). Marking the build as aborted.
Build was aborted

2015-12-04 23:57:11,747 - DEBUG helpers.py:328 -- Executing command: '/sbin/shutdown -Ph now'

Since slave are in bootstrap state at step #4, we can avoid a situation when SSH session hangs on halted node just by replacing warm shutdown by hard VMs destroy.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/254315

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/254315
Committed: https://git.openstack.org/cgit/openstack/fuel-qa/commit/?id=e22d170f9449c2f3d5a042d5d2b448ebb6f4973e
Submitter: Jenkins
Branch: master

commit e22d170f9449c2f3d5a042d5d2b448ebb6f4973e
Author: Artem Panchenko <email address hidden>
Date: Mon Dec 7 19:08:54 2015 +0200

    Destroy slaves in tests for IBP

    Destroy slaves instead of graceful power off in test
    for repeatable provisioning in order to avoid SSH session
    hang.

    Change-Id: I010a78adfff75fb0621354f1225342dcd1a334d0
    Closes-bug: #1523601