USN-5008-2: Avahi vulnerability

USN-5008-1 fixed a vulnerability in avahi. This update provides the corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM. Original advisory details: Thomas Kremer discovered that Avahi incorrectly handled termination signals on the Unix socket. A local attacker could possibly use this issue to cause Avahi to hang, resulting in a denial of service.