Add Spark to list of default plugins in sahara.conf

[Chad Roberts]

The Spark plugin has been around for awhile now. The image for it is built by default by the DIB. Given that, it should probably be turned on by default in the sahara configs.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/124786

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/124786
Committed: https://git.openstack.org/cgit/openstack/sahara/commit/?id=3225dbb4edc48efc28f9e96daabc56939dd73077
Submitter: Jenkins
Branch: master

commit 3225dbb4edc48efc28f9e96daabc56939dd73077
Author: Chad Roberts <email address hidden>
Date: Mon Sep 29 11:51:18 2014 -0400

    Adding Spark to the list of default plugins

    Spark is now present as a plugin with the default
    installation of Sahara.

    Change-Id: I94a26f721839386e7d04668a0054ba583cf1a698
    Closes-Bug: #1375316