USN-4737-2: Bind vulnerability

USN-4737-1 fixed a vulnerability in Bind. This update provides
the corresponding update for Ubuntu 12.04 ESM and Ubuntu 14.04 ESM.

Original advisory details:

It was discovered that Bind incorrectly handled GSSAPI security policy
negotiation. A remote attacker could use this issue to cause Bind to crash,
resulting in a denial of service, or possibly execute arbitrary code. In
the default installation, attackers would be isolated by the Bind AppArmor
profile.