add attach_queue to tun_socket

Modeled after http://oss.tresys.com/pipermail/refpolicy/2013-January/006283.html

Addresses the following kernel error message:

  <6>[    3.855423] SELinux:  Permission attach_queue in class tun_socket not defined in policy.
  <6>[    3.862482] SELinux: the above unknown classes and permissions will be denied
  <7>[    3.869668] SELinux:  Completing initialization.

Change-Id: Iad87fcd5348d121a808dbe7ae3c63f8c90fc09fc