1) Add initialization for trx->xid in InnoDB trx pool
2) Add server UUID in the XID of InnoDB SR transactions
3) Modify trx_recover_for_mysql_callback() so that recovered InnoDB SR
transactions are not made visible to MySQL as recovered XA transactions.
4) Modify how SR transactions are detected and the wsrep_is_sr flag is
set for InnoDB SR transactions.