[CentOS] vsftpd rejects users set to nologin

[Kenneth Porter]

More digging (now that I have a better handle on how to ask the question) 
reveals this bug against documentation and release notes for 7.6 to alert 
updaters about this breaking change for vsftpd:

https://bugzilla.redhat.com/show_bug.cgi?id=1647485

The last comment there, #15 by "Roy":

> For a workaround to vsftpd login failures that doesn't expose your system
> to the cited CVE, and retains the benefits of system user account
> separation, read from "Virtual users with TLS/SSL/FTPS and a common
> upload directory - Complicated vsftpd" on
> https://ubuntuforums.org/showthread.php?t=518293, but implement home
> directories using the section "System users as a virtual user with
> non-system password" as a guide.