httpd failed to start correctly during testing, causing all mod_cluster test to fail.
from the log:

[Tue Jul 30 07:56:13.860687 2019] [core:notice] [pid 2113:tid 3078526800] SELinux policy enabled; httpd running as context unconfined_u:unconfined_r:unconfined_java_t:s0-s0:c0.c1023
[Tue Jul 30 07:56:13.862327 2019] [md:debug] [pid 2113:tid 3078526800] mod_md.c(1013): AH10070: initializing post config dry run
[Tue Jul 30 07:56:13.862345 2019] [md:debug] [pid 2113:tid 3078526800] mod_md.c(361): AH10037: server seems not reachable via http: (port 80->80) and not reachable via https: (port 443->443)
[Tue Jul 30 07:56:13.862516 2019] [md:error] [pid 2113:tid 3078526800] (13)Permission denied: init fs store at /opt/rh/jbcs-httpd24/root/var/lib/httpd/md
[Tue Jul 30 07:56:13.862554 2019] [md:error] [pid 2113:tid 3078526800] (13)Permission denied: AH10046: setup store for /opt/rh/jbcs-httpd24/root/var/lib/httpd/md
[Tue Jul 30 07:56:13.862561 2019] [md:error] [pid 2113:tid 3078526800] (13)Permission denied: AH10072: setup md registry
AH00016: Configuration Failed

Note:
if it's installed manually as root, which is the case for rpm tests; it works as expected.