phase 3 of the development: state transfers and more tests
Make SST work with the binlog in InnoDB, both when all nodes
use it and in a cluster where some nodes use a file binlog.
Several new mtr tests.
Known issues: joiner using binlog-in-engine binlog receiving SST
from a donor using file binlog has no binlog GTID position in the
wsrep domain until it binlogs a transaction.
joiner using binlog files receiving rsync SST from a donor using
binlog-in-engine, will keep the copied .ibb files.
cd614a1e1d