Change debian mariadb backup tool to mariabackup

Current debian stretch use mariadb 10.1.26 which integrates
a backup tool call 'MariaDB Backup' [1]. It is based on
Percona XtraBackup and support full backup capability for
MariaDB Server that includes encrypted and compressed data.

This patch also fixs muti-node deployment failed on Debian
aarch64. Percona's repo has no XtraBackup package for Debian
aarch64. In such case we can use MariaDB builtin backup tool
'MariaDB Backup'.

[1] https://mariadb.com/kb/en/library/mariadb-backup-overview/

Change-Id: I7271d3f93b41d4839670a2c4a358744333411cd7

ansible/roles/mariadb/templates/galera.cnf.j2

 {%- set wsrep_driver = '/usr/lib/galera/libgalera_smm.so' if kolla_base_distro in ['debian', 'ubuntu'] else '/usr/lib64/galera/libgalera_smm.so' %}
+{% set sst_method = 'mariabackup' if kolla_base_distro in ['debian'] else 'xtrabackup-v2' %}
 
 [client]
 default-character-set=utf8
@@ -33,7 +34,7 @@ wsrep_sst_receive_address={{ api_interface_address }}:{{ mariadb_sst_port }}
 wsrep_provider={{ wsrep_driver }}
 wsrep_cluster_name="{{ database_cluster_name }}"
 wsrep_node_name={{ ansible_hostname }}
-wsrep_sst_method=xtrabackup-v2
+wsrep_sst_method={{ sst_method }}
 wsrep_sst_auth={{ database_user }}:{{ database_password }}
 wsrep_slave_threads=4
 wsrep_notify_cmd=/usr/local/bin/wsrep-notify.sh