Enable xtrabackup methods for Galera SST

- Enable xtrabackup as SST method for Galera
- Turn off perfomance_schema on
- Remove old openssl packet
- Slightly decrease RAM for innodb_buffer_pool_size
- Set 1M buffer for send/recieve socket for socat to
  speed up SST between nodes

Change-Id: I9b0b5eee6deab366324f1f808e32f64e290b444e
Implements: bp/galera-improvements
Closes-Bug: 1354479
Merge "Enable xtrabackup methods for Galera SST"