Add theme settings for Horizon Mitaka and newer

Issue: PROD-20920

Change-Id: I8b2c8a0f7f3f1218bf7d85a12da198628c53db0a
diff --git a/tests/pillar/single.sls b/tests/pillar/single.sls
index a364e2e..08f6794 100644
--- a/tests/pillar/single.sls
+++ b/tests/pillar/single.sls
@@ -55,3 +55,16 @@
       enable_fip_topology_check: False
     default_domain: default
     multidomain: False
+    themes:
+      default: default
+      directory: themes
+      cookie_name: theme
+      available:
+        default:
+          name: "Default"
+          description: "Default style theme"
+          path: "themes/default"
+        material:
+          name: "Material"
+          description: "Google's Material Design style theme"
+          path: "themes/material"