controller daemon for processing dbus commands in ap-daemons uses a symlink on the stateful file system, which is being prohibited by CL:472908 for security reasons (see https://goo.gl/8xICW6 for context and rationale).

An exception will be added in the short term for this part of the file system (/var/lib/ap), but should be removed in the future when symlink usage is eliminated.

CODE: https://cs.corp.google.com/chromeos_internal/src/platform/ap-daemons/controller/controller_daemon_base.cc?rcl=944939b36a4a7671bcb61dfad3be16277a68aa22&l=287