Galera cluster - cannot start MariaDB (CentOS7)

I'm trying to install a Galera cluster with 3 mariadb VM's (all of them CentOS 7). I've never done this before, so I was following this guide:

http://tunnelix.com/mariadb-galera-cluster-installation/

The problem is that after I enter my settings on the /etc/my.cnf.d/server.cnf file (step 6 on the guide), I can't start MariaDB:

[root@galera1 ~]# systemctl start mariadb
Job for mariadb.service failed. See 'systemctl status mariadb.service' and 'journalctl -xn' for details.

[root@galera1 ~]# systemctl status -l mariadb
mariadb.service - MariaDB database server
   Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled)
  Drop-In: /etc/systemd/system/mariadb.service.d
           └─migrated-from-my.cnf-settings.conf
   Active: failed (Result: exit-code) since Thu 2016-10-27 12:23:42 WEST; 5s ago
  Process: 3435 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR= ||   VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ]   && systemctl set-environment _WSREP_START_POSITION=$VAR || exit 1 (code=exited, status=1/FAILURE)
  Process: 3433 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)

Oct 27 12:23:39 galera1.syone.int sh[3435]: 2016-10-27 12:23:39 140598747605120 [Note] InnoDB: Waiting for purge to start
Oct 27 12:23:39 galera1.syone.int sh[3435]: 2016-10-27 12:23:39 140598747605120 [Note] InnoDB:  Percona XtraDB (http://www.percona.com) 5.6.32-78.1 started; log sequence number 1617490
Oct 27 12:23:39 galera1.syone.int sh[3435]: 2016-10-27 12:23:39 140598747605120 [Warning] InnoDB: Skipping buffer pool dump/restore during wsrep recovery.
Oct 27 12:23:39 galera1.syone.int sh[3435]: 2016-10-27 12:23:39 140598747605120 [Note] Plugin 'FEEDBACK' is disabled.
Oct 27 12:23:39 galera1.syone.int sh[3435]: 2016-10-27 12:23:39 140598747605120 [Note] Server socket created on IP: '0.0.0.0'.
Oct 27 12:23:39 galera1.syone.int sh[3435]: 2016-10-27 12:23:39 140598747605120 [Note] WSREP: Recovered position: 00000000-0000-0000-0000-000000000000:-1
Oct 27 12:23:42 galera1.syone.int sh[3435]: WSREP: Failed to recover position: ''
Oct 27 12:23:42 galera1.syone.int systemd[1]: mariadb.service: control process exited, code=exited status=1
Oct 27 12:23:42 galera1.syone.int systemd[1]: Failed to start MariaDB database server.
Oct 27 12:23:42 galera1.syone.int systemd[1]: Unit mariadb.service entered failed state.

Here's the content of the my.cnf file:

[galera]
Mandatory settings
wsrep_on=ON
wsrep_provider=/usr/lib64/galera/libgalera_smm.so
wsrep_cluster_address='gcomm://'
wsrep_cluster_name='galera'
wsrep_node_address='10.1.40.83'
wsrep_node_name='galera1'
wsrep_sst_method=rsync

binlog_format=row
default_storage_engine=InnoDB
innodb_autoinc_lock_mode=2
Allow server to accept connections on all interfaces.
bind-address=0.0.0.0

I've been searching for a solution about this error and the only thing that I found was a bug (https://jira.mariadb.org/browse/MDEV-10396), but I confirmed the /usr/bin/galera_recovery script, and it already has that fix.

The weird part is these 2 lines on the logs:

Oct 27 12:23:39 galera1.syone.int sh[3435]: 2016-10-27 12:23:39 140598747605120 [Note] WSREP: Recovered position: 00000000-0000-0000-0000-000000000000:-1
Oct 27 12:23:42 galera1.syone.int sh[3435]: WSREP: Failed to recover position: ''

He gets the WSREP position, but it fails to get it...? This doesn't make any sense for me. What am I missing?

Thanks!