Testcase 

1) /ssd/ramesh/workdir/pxc/bin/mysqld --defaults-file=n1.cnf  --basedir=/ssd/ramesh/workdir/pxc --datadir=/ssd/ramesh/workdir/pxc/node0 \
  --wsrep-provider=/ssd/ramesh/workdir/pxc/lib/libgalera_smm.so \
  --wsrep_cluster_address=gcomm:// --wsrep_node_incoming_address=127.0.0.1 \
  --wsrep_provider_options=gmcast.listen_addr=tcp://127.0.0.1:22008 \
  --wsrep_sst_method=xtrabackup-v2 --wsrep_sst_auth=root: \
  --wsrep_node_address=127.0.0.1 \
  --log-error=/ssd/ramesh/workdir/pxc/node0/node0.err \
  --socket=/ssd/ramesh/workdir/pxc/node0/socket.sock \
  --port=22000 --server-id=1 --wsrep_slave_threads=2 &


$ cat n1.cnf 
[mysqld]
innodb_autoinc_lock_mode=2
innodb_locks_unsafe_for_binlog=1

ssl-ca=/ssd/ramesh/workdir/pxc/node0/ca.pem
ssl-cert=/ssd/ramesh/workdir/pxc/node0/server-cert.pem
ssl-key=/ssd/ramesh/workdir/pxc/node0/server-key.pem

[xtrabackup]
user=root
password=
$ 

2) rm -rf node1/grastate.dat

3) /ssd/ramesh/workdir/pxc/bin/mysqld --defaults-file=n2.cnf --basedir=/ssd/ramesh/workdir/pxc --datadir=/ssd/ramesh/workdir/pxc/node1 \
   --wsrep-provider=/ssd/ramesh/workdir/pxc/lib/libgalera_smm.so \
   --wsrep_cluster_address=gcomm://127.0.0.1:22008,gcomm://127.0.0.1:22108 \
   --wsrep_node_incoming_address=127.0.0.1 --wsrep_provider_options=gmcast.listen_addr=tcp://127.0.0.1:22108 \
   --wsrep_sst_method=xtrabackup-v2 --wsrep_sst_auth=root: \
   --wsrep_node_address=127.0.0.1 \
   --log-error=/ssd/ramesh/workdir/pxc/node1/node1.err \
   --socket=/ssd/ramesh/workdir/pxc/node1/socket.sock \
   --port=22100 --server-id=1 --wsrep_slave_threads=2 &


[ramesh@qaserver-04 pxc]$ cat n2.cnf 
[mysqld]
innodb_autoinc_lock_mode=2
innodb_locks_unsafe_for_binlog=1
ssl-ca=/ssd/ramesh/workdir/pxc/node1/ca.pem
ssl-cert=/ssd/ramesh/workdir/pxc/node1/server-cert.pem
ssl-key=/ssd/ramesh/workdir/pxc/node1/server-key.pem

[xtrabackup]
user=root
password=
[ramesh@qaserver-04 pxc]$ 




$ cat node0/innobackup.backup.log 
161201 11:41:13 innobackupex: Starting the backup operation

IMPORTANT: Please check that the backup run completes successfully.
           At the end of a successful backup run innobackupex
           prints "completed OK!".

161201 11:41:13 Connecting to MySQL server host: localhost, user: root, password: set, port: 0, socket: /ssd/ramesh/workdir/pxc/node0/socket.sock
Using server version 5.6.32-78.1-25.17
innobackupex version 2.3.6 based on MySQL server 5.6.24 Linux (x86_64) (revision id: 7686bfc)
xtrabackup: uses posix_fadvise().
xtrabackup: cd to /ssd/ramesh/workdir/pxc/node0/
xtrabackup: open files limit requested 0, set to 1024
xtrabackup: using the following InnoDB configuration:
xtrabackup:   innodb_data_home_dir = ./
xtrabackup:   innodb_data_file_path = ibdata1:12M:autoextend
xtrabackup:   innodb_log_group_home_dir = ./
xtrabackup:   innodb_log_files_in_group = 2
xtrabackup:   innodb_log_file_size = 50331648
161201 11:41:13 >> log scanned up to (1626341)
xtrabackup: Generating a list of tablespaces
161201 11:41:13 [01] Streaming ./ibdata1
[..]
161201 11:41:14 Executing UNLOCK BINLOG
161201 11:41:14 Executing UNLOCK TABLES
161201 11:41:14 All tables unlocked
161201 11:41:14 Backup created in directory '/tmp/tmp.JWwYzi3l5n'
161201 11:41:14 [00] Streaming backup-my.cnf
161201 11:41:14 [00]        ...done
161201 11:41:14 [00] Streaming xtrabackup_info
161201 11:41:14 [00]        ...done
xtrabackup: Transaction log of lsn (1626341) to (1626341) was copied.
161201 11:41:14 completed OK!
$