USN-4616-2: AccountsService vulnerabilities

USN-4616-1 fixed several vulnerabilities in AccountsService. This update provides the corresponding update for Ubuntu 14.04 ESM. Original advisory details: Kevin Backhouse discovered that AccountsService incorrectly dropped privileges. A local user could possibly use this issue to cause AccountsService to crash or hang, resulting in a denial of service. (CVE-2020-16126) Matthias Gerstner discovered that AccountsService incorrectly handled certain path checks. A local attacker could possibly use this issue to read arbitrary files. (CVE-2018-14036)