Samba 4.3+ "logging" smb.conf option can suppress logging to files, but they are still created and stay empty. Once this minor bug is solved my old bug https://bugzilla.samba.org/show_bug.cgi?id=9955 can be closed. (CentOS 7.4 here, samba-4.6.2-11.el7_4.x86_64)