reverted commit 6286442 to avoid promoting grain lookup in pillars

pillar.example

@@ -12,10 +12,10 @@ postfix:
   smtpd_tls_session_cache_database: btree:${data_directory}/smtpd_scache
   smtp_tls_session_cache_database: btree:${data_directory}/smtp_scache
 
-  myhostname: {{ grains['fqdn'] }}
+  myhostname: localhost
   alias_maps: hash:/etc/aliases
   alias_database: hash:/etc/aliases
-  mydestination: {{ grains['fqdn'] }}, localhost.localdomain, {{  grains['domain'] }}
+  mydestination: localhost, localhost.localdomain
   relayhost: 
   mynetworks: 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
   mailbox_size_limit: 0