Fix Ubuntu idempotency and pkg upgrades

The Ubuntu packages for panko-api now defaults
to installing with Apache and WSGI so it drops
the vhost files in the directory which the apache
module then removes.

We force them as empty and by that we keep idempotency
but we also dont break package upgrades for panko-api
because the dh-apache helper for deb packging fails if
these files are removed.

This is the same as we've done for keystone, sahara etc.

Change-Id: I4466d14b825a2392594a1b86b08aeed5793c77b8

manifests/panko.pp

@@ -39,6 +39,21 @@ class openstack_integration::panko {
     enabled      => true,
     service_name => 'httpd',
   }
+  # NOTE(tobias-urdin): The panko-api package in Ubuntu installs the apache vhosts which we
+  # not need but we keep them as empty to not break package upgrades.
+  if ($::operatingsystem == 'Ubuntu') and (versioncmp($::operatingsystemmajrelease, '18') >= 0) {
+    ensure_resource('file', '/etc/apache2/sites-available/panko-api.conf', {
+      'ensure'  => 'present',
+      'content' => '',
+    })
+    ensure_resource('file', '/etc/apache2/sites-enabled/panko-api.conf', {
+      'ensure'  => 'present',
+      'content' => '',
+    })
+
+    Package['panko-api'] -> File['/etc/apache2/sites-available/panko-api.conf']
+    -> File['/etc/apache2/sites-enabled/panko-api.conf'] ~> Anchor['panko::install::end']
+  }
   include ::apache
   class { '::panko::wsgi::apache':
     bind_host => $::openstack_integration::config::ip_for_url,