torture: Address race in module cleanup

When performing module cleanups by calling torture_cleanup() the
'torture_type' string in nullified However, callers are not necessarily
done, and might still need to reference the variable. This impacts
both rcutorture and locktorture, causing printing things like:

[   94.226618] (null)-torture: Stopping lock_torture_writer task
[   94.226624] (null)-torture: Stopping lock_torture_stats task

Thus delay this operation until the very end of the cleanup process.
The consequence (which shouldn't matter for this kid of program) is,
of course, that we delay the window between rmmod and modprobing,
for instance in module_torture_begin().

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/locking/locktorture.c

@@ -361,7 +361,7 @@ static void lock_torture_cleanup(void)
 {
 	int i;
 
-	if (torture_cleanup())
+	if (torture_cleanup_begin())
 		return;
 
 	if (writer_tasks) {
@@ -384,6 +384,7 @@ static void lock_torture_cleanup(void)
 	else
 		lock_torture_print_module_parms(cur_ops,
 						"End of test: SUCCESS");
+	torture_cleanup_end();
 }
 
 static int __init lock_torture_init(void)