Low: setup security update (Amazon Linux 2)

Package updates are available for Amazon Linux 2 that fix the following vulnerabilities: CVE-2018-1113: Setup in Fedora and Red Hat Enterprise Linux added /sbin/nologin and /usr/sbin/nologin to /etc/shells. This violates security assumptions made by pam_shells and some daemons which allow access based on a user's shell being listed in /etc/shells. Under some circumstances, users which had their shell changed to /sbin/nologin could still access the system. 1571094: CVE-2018-1113 setup: nologin listed in /etc/shells violates security expectations