[docs] Initial Percona cluster support added

[OpenStack Infra]

https://review.openstack.org/188454
commit 20b5983868da2aa196b884c6c2624d06c6a65aa3
Author: Mykyta Koshykov <email address hidden>
Date: Thu Jun 4 10:53:18 2015 -0500

    Initial Percona cluster support added

    This change adds two new custom_setup_class options to the mysql class.
    With this change, we now support 'percona' and 'percona_packages' to
    be passed to the mysql::server class that will cause percona to be
    used.

    This change adds the use_percona and use_percona_packages params to
    the existing galera class. The 'use_percona' option will cause the
    configuration to use the Linux distrubution classes for the Percona
    installation. This only works with Ubuntu. By setting both 'use_percona'
    and 'use_percona_packages' to true, the puppet configuration will
    use the Percona provided packages for installation. This assumes that
    the Percona packages are available to the system.

    Additionally tests have been added to the galera
    class to ensure that expected resources are configured for both
    the regular packages and the percona packages. By default, the
    existing galera configuration remains the same and assumes the
    use of existing packages.

    Partial blueprint: detach-components-from-controllers
    DocImpact

    Change-Id: I972698a8b2dae4caca6101db6d48bab405e40eae
    Co-Authored-By: Nikita Koshikov <email address hidden>
    Co-Authored-By: Alex Schultz <email address hidden>