Bug #51398 Test "rpl_heartbeat_basic" fails "while waiting for slave_received_heartbeats"

Non-determinism of the test was caused by lack of setting a proper value to hb period,
actually fixed by BUG@50767.

These fixes aim at possible non-determinism in comparison of received
hb events by master and slave in the circular part of the test.
Even though the HB periods ratio was choosen to be as high as 10, it's still incorrect 
to compare number of hb-events basing only a relation between their periods.

Yet another issue is relatively short 60 secs timeout of wait_for_status_var.inc
makes valgrind runs to fail. 
Fixed with deploying wait_for_slave_io_to_start afront of calling wait_for_status_var.

The test is made runnable only with MIXED binlog-format as it has close to 1 min
total exec time and there is nothing format specific in it.

mysql-test/suite/rpl/r/rpl_heartbeat_basic.result

@@ -290,12 +290,10 @@ a	b
 2	on slave
 Heartbeat event received on master
 Heartbeat event received on slave
-Slave has received more events than master (1 means 'yes'): 1
-
 *** Clean up ***
 include/stop_slave.inc
 DROP TABLE t1;
 include/stop_slave.inc
 SET @@global.slave_net_timeout=@restore_slave_net_timeout;
 
-End of 6.0 test
+End of tests

mysql-test/suite/rpl/t/rpl_heartbeat_basic.test

@@ -10,6 +10,12 @@
 # * Circular replication
 #############################################################
 --source include/master-slave.inc
+#
+# The test runs long and does not have any specifics to 
+# binlog_format. It is choosen therefore to run with MIXED mode
+# in order to not slow down much `make test'.
+#
+--source include/have_binlog_format_mixed.inc
 --echo
 
 --echo *** Preparing ***
@@ -462,6 +468,9 @@ EOF
 --enable_reconnect
 --source include/wait_until_connected_again.inc
 --connection slave
+# make sure IO thread has re-connected 
+# due to slow valgrind env the following wait_for_status may time out
+--source include/wait_for_slave_io_to_start.inc
 # Wait until slave_received_heartbeats will be incremented
 let $status_var_value= query_get_value(SHOW STATUS LIKE 'slave_received_heartbeats', Value, 1);
 let $status_var= slave_received_heartbeats;
@@ -470,7 +479,7 @@ let $status_var_comparsion= >;
 --echo Heartbeat event received
 --echo
 
-# Circular replication
+# Circular replication: demonstrating bidirectional hearbeat flow
 --echo *** Circular replication ***
 # Configure circular replication
 --source include/master-slave-reset.inc
@@ -499,15 +508,16 @@ SELECT * FROM t1 ORDER BY a;
 let $master_rcvd_heartbeats_before= query_get_value(SHOW STATUS LIKE 'slave_received_heartbeats', Value, 1);
 --connection slave
 SELECT * FROM t1 ORDER BY a;
-# Wait heartbeat event on master
+
+# Wait for heartbeat event on master
 --connection master
 let $status_var= slave_received_heartbeats;
 let $status_var_value= query_get_value(SHOW STATUS LIKE 'slave_received_heartbeats', Value, 1);
 let $status_var_comparsion= >;
 --source include/wait_for_status_var.inc
 --echo Heartbeat event received on master
-let $master_rcvd_heartbeats= query_get_value(SHOW STATUS LIKE 'slave_received_heartbeats', Value, 1);
-# Wait heartbeat event on slave
+
+# Wait heartbeat events on slave
 --connection slave
 let $status_var= slave_received_heartbeats;
 let $status_var_value= query_get_value(SHOW STATUS LIKE 'slave_received_heartbeats', Value, 1);
@@ -515,11 +525,6 @@ let $status_var_comparsion= >;
 --source include/wait_for_status_var.inc
 --echo Heartbeat event received on slave
 let $slave_rcvd_heartbeats= query_get_value(SHOW STATUS LIKE 'slave_received_heartbeats', Value, 1);
-# Heartbeat period on slave less than on master therefore number of received events on slave
-# should be greater than on master
-let $result= query_get_value(SELECT ($slave_rcvd_heartbeats DIV $master_rcvd_heartbeats) > 1 AS Result, Result, 1);
---echo Slave has received more events than master (1 means 'yes'): $result
---echo
 
 #
 # Clean up and restore system variables
@@ -533,5 +538,5 @@ DROP TABLE t1;
 SET @@global.slave_net_timeout=@restore_slave_net_timeout;
 --echo
 
-# End of 6.0 test
---echo End of 6.0 test
+# End of tests
+--echo End of tests