Check "cyrus" Exim router before "localuser"

If Exim checks the default "localuser" router before our custom
"cyrus" router, then the lpmqtt account's messages will get
delivered to its system mbox rather than its Cyrus IMAP inbox. To
fix this ordering problem, disable the default localuser router and
define our own after cyrus.

Change-Id: I08b024f1b4097bf651b4c3ed97a319f579869ce4
Depends-On: https://review.openstack.org/577893

modules/openstack_project/manifests/firehose.pp

@@ -72,6 +72,7 @@ class openstack_project::firehose (
   class {'::exim':
     sysadmins => $sysadmins,
     local_domains => "@:firehose.openstack.org",
+    default_localuser_router => false,
     routers  => [
       {'cyrus' => {
         'driver'                     => 'accept',
@@ -79,6 +80,12 @@ class openstack_project::firehose (
         'local_part_suffix'          => '+*',
         'local_part_suffix_optional' => true,
         'transport'                  => 'cyrus',
+      }},
+      {'localuser' => {
+        'driver'               => 'accept',
+        'check_local_user'     => true,
+        'transport'            => 'local_delivery',
+        'cannot_route_message' => 'Unknown user',
       }}
     ],
     transports => [