selinux: clean up avc node cache when disabling selinux

Added a call to free the avc_node_cache when inside selinux_disable because
it should not waste resources allocated during avc_init if SELinux is disabled
and the cache will never be used.

Signed-off-by: Thomas Liu <tliu@redhat.com>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index 7823e84..236aaa2 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -970,3 +970,9 @@
 {
 	return avc_cache.latest_notif;
 }
+
+void avc_disable(void)
+{
+	if (avc_node_cachep)
+		kmem_cache_destroy(avc_node_cachep);
+}