Close imap ports on firehose

The imap server on firehose.openstack.org doesn't actually need
external connectivity since the lpmqtt daemon is running on the same
host. This commit removes the imap ports from the firehose port list.

Change-Id: I5a9aaafe566dbd3e4e2e2f5790aec812db99f0ee

manifests/site.pp

@@ -498,7 +498,7 @@ node /^elasticsearch0[1-7]\.openstack\.org$/ {
 # Node-OS: xenial
 node /^firehose\d+\.openstack\.org$/ {
   class { 'openstack_project::server':
-    iptables_public_tcp_ports => [22, 25, 80, 143, 993, 1883, 8080, 8883],
+    iptables_public_tcp_ports => [22, 25, 80, 1883, 8080, 8883],
     sysadmins                 => hiera('sysadmins', []),
     manage_exim               => false,
   }