custom yaml file for opstools uses now "siumple" auth mode. There is no auth mode called simple. Fix the mode to basic so it gets set correctly when configured in collectd.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2018:3587