Change-Id: I70f258509b38b2a616be34913c7345d93c2b50ad

The following configuration options added:

    galera_innodb_read_io_threads: 8
    galera_innodb_write_io_threads: 8
    galera_wsrep_slave_threads: 8
    galera_xtrabackup_parallel: 4
    galera_error_log_enabled: false

Change-Id: Id1185c3a38669c37dc88806b4e9955522629ce1c
Related-Bug: https://mirantis.jira.com/browse/PROD-16528

Make max_connections and innodb_buffer_pool_size configurable
through soft params instead of hard.

Change-Id: Id0bb8f6b6091289275864bf4dd6a6890d11b4782

This also installs 2 additional packages (libdbd-mysql and
python-pymysql) that are required for running the collectd plugins.