BREAK FOR SOME QUERIE

A corner case caused slave hang when slave_preserve_commit_order is ON.

ANALYSIS
========
CREATE TABLE t1(c1 INT PRIMARY KEY, c2 INT, INDEX(c2)) ENGINE = InnoDB;
INSERT INTO t1 VALUES(1, NULL),(2, 2), (3, NULL), (4, 4), (5, NULL), (6, 6);

INSERT INTO t1 VALUES(7, NULL);
DELETE FROM t1 WHERE c2 <= 3;

On master, the INSERT statement acquires its row lock before DELETE STATEMENT.
Since the INSERT doesn't block the DELETE, Both statements may have same
commit parent which mean they can be applied parallel on slave.

On slave, they will be applied parallel if MTS is ON. There is a chance that
the DELETE acquires its lock before the INSERT. The DELETE holds a gap lock
on INDEX(c2) which blocks the INSERT statement. The INSERT cannot be applied
unless DELETE is committed or rolled back. And meanwhile the DELETE is waiting
for the INSERT to commit since slave_preserve_commit_order is ON. That is
a deadlock and hangs the slave. Here we call the deadlock as a order commit
deadlock.

FIX
===
A deadlock checking mechanism is introduced. Every time when a transaction
needs to wait for another transaction to release a row lock, innodb will
call a slave function to check if there is an order commit deadlock. If
it founds an order commit deadlock, It will set a deadlock flag to the
slave worker which is holding the row lock. Thereafter, the worker will
roll its transaction back and retry it again.