fix(canal): Preserve binlog filename received in the fake rotate event

[mefcorvi]

The name of a binlog file received in the fake rotate event must be preserved as it was discussed in #406.

The decision is based on comments in
https://github.com/mysql/mysql-server/blob/8e797a5d6eb3a87f16498edcb7261a75897babae/sql/rpl_binlog_sender.h#L235

... It contains the name of the binlog we are going to
    send to the slave.
    Faked rotate event is required in a few cases, so slave can know which
    binlog the following events are from.
  - The binlog file slave requested is Empty. E.g.
    "CHANGE MASTER TO MASTER_LOG_FILE='', MASTER_LOG_POS=4", etc.
  - The position slave requested is exactly the end of a binlog file.
  - Previous binlog file does not include a rotate event.
    It happens when server is shutdown and restarted.
  - The previous binary log was GTID-free (does not contain a
    Previous_gtids_log_event) and the slave is connecting using
    the GTID protocol.

Closes #406

[siddontang]

thanks @mefcorvi

can we add a test to cover this?

[mefcorvi]

can we add a test to cover this?

I think I can cover the first case "The binlog file slave requested is Empty", but for other cases I need to be able to manage the mysql server from the tests, i.e. shut it down, restart, reconfigure. Can you advise the simplest way to do that?