r/samba-dc: Configure samba logging

Send logs to the systemd journal for easier viewing and disable logging
to a file.  Also, the `samba_dc_log_level` variable can control the log
level (0-10, 0 being off, 10 being insane debugging).

roles/samba-dc/templates/smb.conf.j2

@@ -4,6 +4,11 @@
 	realm = {{ krb5_realm }}
 	server role = active directory domain controller
 	workgroup = {{ workgroup }}
+
+	timestamp logs = no
+	logging = systemd file@0
+	log level = {{ samba_dc_log_level }}
+
 {% if samba_dc_use_rfc2307 %}
 	idmap_ldb:use rfc2307 = yes
 {% endif %}