refs codership/mysql-wsrep#184
refs codership/mysql-wsrep#184

- Adds runtime check wsrep_on(), to not interfere with default
  innodb behavior.

flynn1973/mariadb-aix,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,natsys/mariadb_10.2,flynn1973/mariadb-aix,flynn1973/mariadb-aix,flynn1973/mariadb-aix,natsys/mariadb_10.2,flynn1973/mariadb-aix,ollie314/server,ollie314/server,ollie314/server,natsys/mariadb_10.2,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,ollie314/server,flynn1973/mariadb-aix,flynn1973/mariadb-aix,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,ollie314/server,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix