The "get_master_version_and_clock(...)" function in sql/slave.cc ignores 
error and passes directly when queries fail, or queries succeed 
but the result retrieved is empty.
  
The "get_master_version_and_clock(...)" function should try to reconnect master
if queries fail because of transient network problems, and fail otherwise.
The I/O thread should print a warning if the some system variables do not 
exist on master (very old master)

mysql-test/extra/rpl_tests/rpl_get_master_version_and_clock.test:
  Added test file for bug #45214
mysql-test/suite/rpl/r/rpl_get_master_version_and_clock.result:
  Added test result for bug #45214
mysql-test/suite/rpl/t/rpl_get_master_version_and_clock.test:
  Added test file for bug #45214
sql/slave.cc:
  The 'is_network_error()' function is added for checking if the error is caused by network.
  Added a new return value (2) to 'get_master_version_and_clock()' function result set 
  to indicate transient network errors when queries fail, and the caller should 
  try to reconnect in this case.