Skip backports for buster

This is a follow-on to I39cb9dc0aa52cf5b20545baf4acacc21c5459f2a; as
buster has no backports we need to skip this in the reprepro
configuration.  It's a bit hacky, but we can revert when it is
available.

Change-Id: I60e231f23999d0af9c899a30822c71702befb2bd

modules/openstack_project/manifests/mirror_update.pp

@@ -59,11 +59,12 @@ class openstack_project::mirror_update (
 
   ### Debian mirror ###
   ::openstack_project::reprepro { 'debian-reprepro-mirror':
-    confdir       => '/etc/reprepro/debian',
-    basedir       => '/afs/.openstack.org/mirror/debian',
-    distributions => 'openstack_project/reprepro/distributions.debian.erb',
-    updates_file  => 'puppet:///modules/openstack_project/reprepro/debuntu-updates',
-    releases      => ['stretch', 'buster'],
+    confdir            => '/etc/reprepro/debian',
+    basedir            => '/afs/.openstack.org/mirror/debian',
+    distributions      => 'openstack_project/reprepro/distributions.debian.erb',
+    updates_file       => 'puppet:///modules/openstack_project/reprepro/debuntu-updates',
+    releases           => ['stretch', 'buster'],
+    skip_backports_for => ['buster'],
   }
 
   cron { 'reprepro debian':

modules/openstack_project/manifests/reprepro.pp

@@ -8,6 +8,7 @@ define openstack_project::reprepro (
   $updates_file = undef,
   $options_template = 'openstack_project/reprepro/options.erb',
   $releases = [],
+  $skip_backports_for = [],
 ) {
   file { "$confdir":
     ensure => directory,

modules/openstack_project/templates/reprepro/distributions.debian.erb

@@ -23,6 +23,7 @@ Contents: .gz
 Update: debian
 Log: <%= @logdir %>/debian-<%= release %>-updates.log
 
+<% if not @skip_backports_for.include?(release) %>
 Origin: Debian Backports
 Label: Debian Backports
 Suite: <%= release %>-backports
@@ -36,5 +37,6 @@ UDebComponents: main
 Contents: .gz
 Update: debian
 Log: <%= @logdir %>/debian-<%= release %>-backports.log
+<% end -%>
 
 <% end -%>