BUG#37493: rpl_trunc_temp.test nondeterministic

Problem: the test waits for a 'DROP TEMPORARY TABLE' event to
appear in the master's binlog, then checks on the slave whether
the number of temporary tables has decreased. The slave does
not sync, causing a race.
Fix: check for the 'DROP TEMPORARY TABLE' event on slave
instead of on master.


mysql-test/suite/rpl/t/rpl_trunc_temp.test:
  - Fixed BUG#37493 by waiting for the event on the slave
  instead of on the master.
  - Added comments.

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

-# Requires statement logging
+# ==== Purpose ====
+#
+# Verify that Slave_open_temp_tables is increased when a temporary
+# table is opened on the slave, and decreased when a temporary table
+# is closed on the slave, and that it is preserved during 'DELETE FROM
+# table' and 'TRUNCATE table'.
+#
+# ==== Method ====
+#
+# Create a temporary table on master, insert rows, and try:
+#  - delete rows from the table
+#  - truncate the table
+#  - drop the table
+#
+# ==== Related bugs ====
+#
+# BUG#17137 Running "truncate table" on temporary table leaves the table open on a slave
+#
+# Bug in this test: BUG#37493: rpl_trunc_temp.test nondeterministic
+
+
+# Requires statement-based logging since temporary tables are not
+# logged in row-based logging
 -- source include/have_binlog_format_mixed_or_statement.inc
 
 source include/master-slave.inc;
 
-#
-# Bug#17137 Running "truncate table" on temporary table
-# leaves the table open on a slave
-#
-
 create temporary table t1 (n int);
 insert into t1 values(1);
 sync_slave_with_master;
@@ -28,13 +45,10 @@ show status like 'Slave_open_temp_tables';
 # Disconnect the master, temp table on slave should dissapear
 disconnect master;
 
-connection master1;
-# Wait until drop of temp tables appers in binlog
+connection slave;
+
+# Wait until drop of temp tables appers in slave's binlog
 let $wait_binlog_event= DROP;
 source include/wait_for_binlog_event.inc;
 
-connection slave;
 show status like 'Slave_open_temp_tables';
-
-
-# End of 4.1 tests