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. Restarting master server can bring two problems as following:

1. The time out error is encountered sporadically. The slave I/O thread tries 
   to reconnect master ten times, which is set in my.cnf. So in the test 
   framework sporadically the slave I/O thread really stoped when it can't 
   reconnect to master in the ten times successfully before the master starts, 
   then the time out error will be encountered while waiting for the slave to 
   start.

2. These warnings and errors are produced in server log file when 
   the slave I/O thread tries to get the values of the UNIX_TIMESTAMP, 
   SERVER_ID from master under the transient network disconnection.

To fix problem 1, increase the master retry count to sixty times, 
so that the slave I/O thread has enough time to reconnect master 
successfully.
To fix problem 2, suppress these warnings and errors by mtr suppression, 
because they are expected.