Why don't you use Sernet Enterprise Samba?
(...) they do not provide RPMs for RHEL/CentOS 7. So this seems not to be an option.
As someone said before, you don't need to use "the latest and greatest" to run a functional service... On a production environment that is even often undesirable until things settle down...
Anyway, Sernet also provides a source rpm. Why not build up from that base?