Bug#50596 Spurious test failures in perfschema.dml_mutex_instances

Fixed the dml_mutex_instances and dml_rwlock_instances to be more reliable.
In particular, the tests may not assume a mutex or rwlock is never locked.

mysql-test/suite/perfschema/r/dml_mutex_instances.result

 select * from performance_schema.MUTEX_INSTANCES limit 1;
 NAME	OBJECT_INSTANCE_BEGIN	LOCKED_BY_THREAD_ID
-#	#	NULL
+#	#	#
 select * from performance_schema.MUTEX_INSTANCES
 where name='FOO';
 NAME	OBJECT_INSTANCE_BEGIN	LOCKED_BY_THREAD_ID

mysql-test/suite/perfschema/r/dml_rwlock_instances.result

 select * from performance_schema.RWLOCK_INSTANCES limit 1;
 NAME	OBJECT_INSTANCE_BEGIN	WRITE_LOCKED_BY_THREAD_ID	READ_LOCKED_BY_COUNT
-#	#	NULL	0
+#	#	#	#
 select * from performance_schema.RWLOCK_INSTANCES
 where name='FOO';
 NAME	OBJECT_INSTANCE_BEGIN	WRITE_LOCKED_BY_THREAD_ID	READ_LOCKED_BY_COUNT

mysql-test/suite/perfschema/t/dml_mutex_instances.test

@@ -18,7 +18,7 @@
 --source include/not_embedded.inc
 --source include/have_perfschema.inc
 
---replace_column 1 # 2 #
+--replace_column 1 # 2 # 3 #
 select * from performance_schema.MUTEX_INSTANCES limit 1;
 
 select * from performance_schema.MUTEX_INSTANCES

mysql-test/suite/perfschema/t/dml_rwlock_instances.test

@@ -18,7 +18,7 @@
 --source include/not_embedded.inc
 --source include/have_perfschema.inc
 
---replace_column 1 # 2 #
+--replace_column 1 # 2 # 3 # 4 #
 select * from performance_schema.RWLOCK_INSTANCES limit 1;
 
 select * from performance_schema.RWLOCK_INSTANCES