Performance tests are broken by requirements of NetworkX

[Alexander Kislitsky]

Performance tests is broken:

Downloading/unpacking networkx>=1.10 (from -r /home/jenkins/workspace/nailgun_performance_tests/nailgun/requirements.txt (line 37))
  Running setup.py (path:/home/jenkins/workspace/nailgun_performance_tests/nailgun/.tox/py26/build/networkx/setup.py) egg_info for package networkx
    NetworkX requires Python 2.7 or later (2.6 detected).

We are going to use CentOs 7 on the master node so I guess we should switch perf tests on Python2.7

Or as wrokaround for this issue can be fixed by pinning NetworkX version in the nailgun/requirements.txt:
networkx>=1.8,<1.10

[Aleksandra Fedorova (bookwar)]

In CI configuration we use virtual env with Python 2.7.

py26 env is enabled by run_tests.sh script and should be fixed there.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/255288

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/255288
Committed: https://git.openstack.org/cgit/openstack/fuel-web/commit/?id=30f0f8007b10e9b25229d64cccd4a80d6c8cd8e8
Submitter: Jenkins
Branch: master

commit 30f0f8007b10e9b25229d64cccd4a80d6c8cd8e8
Author: Alexander Kislitsky <email address hidden>
Date: Wed Dec 9 17:36:20 2015 +0300

    Tox python env changed to py27 in run_tests.sh

    After moving to the CentOS 7 we have no python26 env.

    Change-Id: Ia9ad4438ebfd2f6c6cdc1aaebae4f52f96a333c7
    Closes-Bug: #1523397