gate-fuel-library-tasks configuration needs update

[Matthew Mosesohn]

https://review.openstack.org/#/c/241164/ was committed on Nov 3 and https://ci.fuel-infra.org/job/verify-fuel-library-tasks/ was updated, but https://ci.fuel-infra.org/job/gate-fuel-library-tasks/ was never fixed. It's failing on every task.

The config needs to contain this information:
set -ex

VENV=${WORKSPACE}_VENV
virtualenv -p python2.6 --clear ${VENV}
source ${VENV}/bin/activate || exit 1

pip install "tox>=1.8"

/bin/bash ${WORKSPACE}/utils/jenkins/tasks_run_tests.sh

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

Fix proposed to branch: master
Change author: Matthew Mosesohn <email address hidden>
Review: https://review.fuel-infra.org/13932

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

Reviewed: https://review.fuel-infra.org/13932
Submitter: Dmitry Kaigarodsev <email address hidden>
Branch: master

Commit: 52964b71e10e42e4506881be86b72807bd9cbe36
Author: Matthew Mosesohn <email address hidden>
Date: Mon Nov 16 12:23:05 2015

Update fuellib tasks job requirements

fuel_library_tasks now requires tox and
has its own tox config to install requirements.

Change-Id: I7ce3020c2bb4aae2b20d50b09370bf4aff334f17
Closes-Bug: #1515963