bundles/postfix: only get certificate if actually needed

bundles/letsencrypt/files/domains.txt

@@ -1,5 +1,3 @@
-${node.metadata['hostname']}
-
 % for domain, aliases in sorted(node.metadata.get('letsencrypt/domains', {}).items()):
 ${domain} ${' '.join(sorted(aliases))}
 % endfor

bundles/postfix/metadata.py

@@ -49,7 +49,7 @@ else:
     'letsencrypt/reload_after',
 )
 def letsencrypt(metadata):
-    if not node.has_bundle('letsencrypt'):
+    if not node.has_bundle('letsencrypt') or not node.has_bundle('postfixadmin'):
         raise DoNotRunAgain
 
     result = {
@@ -58,11 +58,8 @@ def letsencrypt(metadata):
         },
     }
 
-    myhostname = metadata.get('postfix/myhostname', None)
-
-    if myhostname and myhostname != metadata.get('hostname'):
     result['domains'] = {
-            myhostname: set(),
+        metadata.get('postfix/myhostname', metadata.get('hostname')): set(),
     }
 
     return {