Post-push fix for BUG#50364.

There was an erroneous parameter when calling flush_master_info
from write_ignored_events_info_to_relay_log which could lead to a
server crash. This happens because the I/O thread releases the
log_lock before calling the flush_master_info.

Set the function to call flush_master_info with third parameter
to true, so that the mutex is properly taken.

sql/slave.cc

@@ -1726,7 +1726,7 @@ static void write_ignored_events_info_to_relay_log(THD *thd, Master_info *mi)
                    " to the relay log, SHOW SLAVE STATUS may be"
                    " inaccurate");
       rli->relay_log.harvest_bytes_written(&rli->log_space_total);
-      if (flush_master_info(mi, TRUE, FALSE))
+      if (flush_master_info(mi, TRUE, TRUE))
         sql_print_error("Failed to flush master info file");
       delete ev;
     }