puppet: Reload postfix on /etc/postfix/virtual changes.

`/etc/postfix/virtual` is of `regexp:` type, not `hash:` type, so
running `postmap` on it has no effect; we need to reload Postfix when
it changes.

http://www.postfix.org/DATABASE_README.html#detect

In the interest of forcing a reload now, optimize the regexes by
eliding the unanchored `.*`s at the beginnings and ends.

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>

puppet/zulip/files/postfix/virtual

@@ -1,3 +1,3 @@
-/.*\+.*@.*/ zulip@localhost
-/.*\..*@.*/ zulip@localhost
-/^mm.*/ zulip@localhost
+/\+.*@/ zulip@localhost
+/\..*@/ zulip@localhost
+/^mm/ zulip@localhost

puppet/zulip/manifests/postfix_localmail.pp

@@ -47,14 +47,7 @@ class zulip::postfix_localmail {
     group   => root,
     source  => 'puppet:///modules/zulip/postfix/virtual',
     require => Package[postfix],
-  }
-  exec {'postmap /etc/postfix/virtual':
-    subscribe   => File['/etc/postfix/virtual'],
-    refreshonly => true,
-    require     => [
-      File['/etc/postfix/main.cf'],
-      Package[postfix],
-    ],
+    notify  => Service['postfix'],
   }
 
   file {'/etc/postfix/transport':