USN-4171-6: Apport regression

USN-4171-1 fixed vulnerabilities in Apport. The update caused a regression when handling configuration files. This update fixes the problem, and also introduces further hardening measures. Original advisory details: Kevin Backhouse discovered Apport would read its user-controlled settings file as the root user. This could be used by a local attacker to possibly crash Apport or have other unspecified consequences. (CVE-2019-11481) Sander Bos discovered a race-condition in Apport during core dump creation. This could be used by a local attacker to...