postfix: Use SASL only for main server

Signed-off-by: Florian Pritz <bluewind@xinu.at>

roles/postfix/templates/main.cf.j2

@@ -135,6 +135,7 @@ unknown_address_reject_code = 550
 
 smtpd_reject_footer = For assistance contact <postmaster@archlinux.org>. Please provide the following information in your problem report: time ($localtime) and client ($client_address).
 
+{% if postfix_server %}
 smtpd_sasl_auth_enable = yes
 smtpd_tls_auth_only = yes
 
@@ -145,6 +146,7 @@ smtpd_sasl_path = /var/run/dovecot/auth-client
 smtpd_tls_received_header = yes
 # needed for SA
 smtpd_sasl_authenticated_header = yes
+{% endif %}
 
 {% if postfix_server %}
 smtpd_sender_login_maps =