Pass nginx packages as extra arguments to aegir installation

Installing aegir tries to use non-fpm php packages even if the
fpm package is already installed. Try to circumvent this behaviour
by passing the extra packages directly to the apt-get command as
suggested in the documentation.

@see https://aegir.readthedocs.io/en/3.x/install/#6-optional-install-with-nginx

manifests/hostmaster.pp

@@ -67,12 +67,20 @@ class aegir::hostmaster (
         'before' => Package['aegir'],
       }
     )
+    $install_options = join($nginx_packages)
   }
+  else {
+    $install_options = ''
+  }
+  # Pass in extra packages through install options for nginx support.
+  # Even with aegir/webserver set in preconfig, apt-get tries to install
+  # with phpX (not fpm).
   package { 'aegir':
-    ensure       => 'installed',
-    name         => $package_name,
-    responsefile => '/etc/dpkg/aegir.response',
-    require      => [
+    ensure          => 'installed',
+    name            => $package_name,
+    responsefile    => '/etc/dpkg/aegir.response',
+    install_options => $install_options,
+    require         => [
       Apt::Source['aegir'],
       Class['apt::update'],
       File['/etc/dpkg/aegir.response']