Unpack webclient into dist subdir

The old webclient tarballs had content in a "dist" subdirectory, but
newer ones do not. So as to avoid webroot contamination as well as
to make sure we copy the correct new content into place, unpack the
tarballs into an empty "dist" subdirectory of the download staging
directory.

Change-Id: I15d1e00c9a0aa752b21b6eeedb29bcd89dc03935

manifests/application.pp

@@ -217,13 +217,25 @@ class storyboard::application (
     onlyif  => "curl -I ${webclient_url} -z ./${webclient_filename} | grep '200 OK'",
   }
 
+  # Create/clean the storyboard-webclient unpack directory
+  file { "${src_root_webclient}/dist":
+    ensure  => directory,
+    recurse => true,
+    purge   => true,
+    force   => true,
+    require => File[$src_root_webclient],
+  }
+
   # Unpack storyboard-webclient
   exec { 'unpack-webclient':
-    command     => "tar -xzf ./${webclient_filename}",
+    command     => "tar -xzf ../${webclient_filename}",
     path        => '/bin:/usr/bin',
     refreshonly => true,
-    cwd         => $src_root_webclient,
-    require     => Exec['get-webclient'],
+    cwd         => "${src_root_webclient}/dist",
+    require     => [
+      File["${src_root_webclient}/dist"],
+      Exec['get-webclient'],
+    ],
     subscribe   => Exec['get-webclient'],
   }