isc-dhcp vulnerabilities

USN-5658-1 fixed several vulnerabilities in DHCP. This update provides
the corresponding update for Ubuntu 14.04 ESM.

Original advisory details:

It was discovered that DHCP incorrectly handled option reference counting.
A remote attacker could possibly use this issue to cause DHCP servers to
crash, resulting in a denial of service. (CVE-2022-2928)

It was discovered that DHCP incorrectly handled certain memory operations.
A remote attacker could possibly use this issue to cause DHCP clients and
servers to consume resources, leading to a denial of service.
(CVE-2022-2929)