Sahara version is hardcoded in ostf test of ceilometer/sahara

[Alexandr Kostrikov]

During run of ostf test 'Ceilometer test to check notifications from Sahara' fails due to hardcode of sahara version.

Error message is:
# 2016-05-19 14:30:53 DEBUG (nmanager) Finding and checking image for Sahara...
2016-05-19 14:30:54 DEBUG (nmanager) Image with tags "vanilla" and "2.6.0" not found.
2016-05-19 14:30:54 DEBUG (nmanager) Image is not correctly registered or it is not registered at all. Correct image for Sahara not found.

Images in nova:
root@node-1:~# nova image-list
+--------------------------------------+-------------------------------------------+--------+--------+
| ID | Name | Status | Server |
+--------------------------------------+-------------------------------------------+--------+--------+
| 35b6e95d-1f04-4dd9-9d48-b7d6b7e429ca | TestVM | ACTIVE | |
| 79bbe99e-49aa-47a8-8cfa-af82e1f5585f | debian-8-m-agent.qcow2 | ACTIVE | |
| 917c0b0c-da43-4f5e-8f0d-f9d5c6149e54 | murano-linux | ACTIVE | |
| c341c0c7-f3e3-4688-aec4-b5a503aae7ff | sahara-liberty-vanilla-2.7.1-ubuntu-14.04 | ACTIVE | |
+--------------------------------------+-------------------------------------------+--------+--------+

Images on ci:
# ls /home/jenkins/workspace/cloud-images
centos-6.4-x86_64-20151213015813.qcow2 oracle-linux-20160408042854.qcow2 sahara-kilo-vanilla-2.6-ubuntu-14.04.qcow2 ubuntu_14_04-murano-agent_stable_juno_26_02_15.qcow2
centos-7.0-x86_64-20151213015813.qcow2 qa-centos-cloud-2016-05-05.qcow2 sahara-liberty-vanilla-2.7.1-ubuntu-14.04.qcow2 ubuntu_14_04-murano-agent_stable_juno.qcow2
centos7_devops_04022016.qcow2 rhel7_04022016.qcow2 savanna-0.3-vanilla-1.2.1-ubuntu-13.04.qcow2
cloud-fedora.qcow2 sahara-juno-hdp-2.0.6-centos-6.5.qcow2 ubuntu-12.04-amd64-20151213015813.qcow2
F17-x86_64-cfntools.qcow2 sahara-juno-vanilla-2.4.1-ubuntu-14.04.qcow2 ubuntu-14.04-amd64-20151213015813.qcow2

Code to check:
https://github.com/openstack/fuel-ostf/blob/master/fuel_health/tests/tests_platform/test_ceilometer.py#L509-L524

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