selftests/ftrace: Add test to remove instance with active event triggers

Add a test to ensure we clean up properly when removing an instance
with active event triggers.

Link: http://lkml.kernel.org/r/c479465b2009397708d6c52c8561e1523c22cd31.1494956770.git.naveen.n.rao@linux.vnet.ibm.com

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

tools/testing/selftests/ftrace/test.d/instances/instance-event.tc

@@ -75,9 +75,13 @@ rmdir foo
 if [ -d foo ]; then
         fail "foo still exists"
 fi
-exit 0
-
 
+mkdir foo
+echo "schedule:enable_event:sched:sched_switch" > foo/set_ftrace_filter
+rmdir foo
+if [ -d foo ]; then
+        fail "foo still exists"
+fi
 
 
 instance_slam() {