LP:702303 - Spurious `use` statements in output from mysqlbinlog --rewrite-db="a->b"

This bug was introduced with the implementation of MWL#36.

Normally, mysqlbinlog suppresses output of `use` statements before statements
like BEGIN, COMMIT, SAVEPOINT, ROLLBACK, as they are not needed.

However, this suppression does not happen when the MWL#36 --rewrite-db option
affects the current database.

Test case:

– source include/have_binlog_format_statement.inc
– source include/have_log_bin.inc
– source include/have_innodb.inc
let $MYSQLD_DATADIR= `select @@datadir`;
create table t1 (a int primary key) engine=innodb;
create database test2;
RESET MASTER;
use test2;
begin;
use test;
insert into t1 values (1);
use test2;
commit;
begin;
use test;
insert into t1 values (2);
use test2;
commit;
use test;
select * from t1 order by a;
flush logs;
--exec $MYSQL_BINLOG $MYSQLD_DATADIR/master-bin.000001 --short-form
-exec $MYSQL_BINLOG $MYSQLD_DATADIR/master-bin.000001 --short-form --rewrite-db="test>foo" -rewrite-db="test2>bar"
drop database test2;
drop table t1;

The expected output is that each mysqlbinlog run should output a single `use`
statement, just before the first INSERT. However, currently, the second run
outputs extra `use` statements around the begin/commit statements.

I will commit a fix for 5.2.