The 'rpl_get_master_version_and_clock' test verifies if the slave I/O
thread tries to reconnect to master when it tries to get the values of
the UNIX_TIMESTAMP, SERVER_ID from master under network disconnection.
So the master server is restarted for making the transient network
disconnection, during the period the COM_REGISTER_SLAVE failures are
produced in server log file when the slave I/O thread tries to
register on master.

To fix the problem, suppress COM_REGISTER_SLAVE failures in server log
file by mtr suppression, because they are expected.