Current dir inside container when use `dockerctl shell <container>` was changed from "/root/" to "/"

[Alexander Kurenyshev]

Previously a command "dockerctl shell <container>" moves us to the "/root" directory inside container.
After some fixes was merged by library team, this command moves us to the "/" directory.
Tests are exactly affected are for a reboot plugin and for a vip reservation plugin which tries to copy files inside non-existing folders [1]
This code is failed [2]
That's why we need to fix our tests to use new path.

[1] https://product-ci.infra.mirantis.net/view/8.0_swarm/job/8.0.system_test.ubuntu.fuel_plugin_reboot/25/console
[2] https://github.com/openstack/fuel-qa/blob/master/fuelweb_test/tests/plugins/plugin_reboot/test_plugin_reboot_task.py#L70-L72

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/239985

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/239985
Committed: https://git.openstack.org/cgit/openstack/fuel-qa/commit/?id=33d0ce86737f04a2ada752b19bc9a6251baa2076
Submitter: Jenkins
Branch: master

commit 33d0ce86737f04a2ada752b19bc9a6251baa2076
Author: Egor Kotko <email address hidden>
Date: Wed Oct 28 17:11:24 2015 +0100

    Fix path to plugin

    Adding full path for plugin creation

    Change-Id: Ife31ee10a76368405859e0f7041e1e1008301be6
    Closes-Bug: #1508527