Use root user in numa_cpu tests

[Ksenia Svechnikova]

Detailed bug description:
On 10.0 ISO the default user for tests were changed, now it's not enough permission for CPU_pinning tests

Steps to reproduce:
        """Check different amount of pinned CPU
        Scenario:
            1. Revert snapshot "basic_env_for_numa_cpu_pinning"
            2. Pin maximum CPU for the nova on the first compute
            3. Pin minimun CPU for the nova on the second compute
            4. Verify setting was successfully applied
            5. Deploy cluster
            6. Check new filters are enabled in nova.conf at controller ===> fail here
            7. Check nova.conf contains pinned CPU at compute
            8. Run OSTF
            9. Boot VM with pinned CPU on the first compute
            10. Boot VM with pinned CPU on the second compute
        Snapshot: cpu_pinning_on_two_compute

Expected results: sshmanager give can open file and check nessasary filters

Actual result: IOError: [Errno 13] Permission denied

[Fuel Devops McRobotson (fuel-devops-robot)]

Fix proposed to branch: master
Change author: Ksenia Demina <email address hidden>
Review: https://review.fuel-infra.org/21124

[Fuel Devops McRobotson (fuel-devops-robot)]

Reviewed: https://review.fuel-infra.org/21124
Submitter: Aleksandra Fedorova <email address hidden>
Branch: master

Commit: ab947200b5d893130fe39cc0e9117b2192a215f5
Author: Ksenia Demina <email address hidden>
Date: Mon May 23 11:19:48 2016

Add root use in cpu_pinning test

Change-Id: Iabf54fe5d04fc70b95844a2ef625038a28bb29ed
Closes-Bug: #1584722

[Ksenia Svechnikova (kdemina)]

Verified, Job become green: https://product-ci.infra.mirantis.net/view/10.0_swarm/job/10.0.system_test.ubuntu.numa_cpu_pinning/34/