Add Salt 2018.3 tests

Change-Id: I0e972ff4c1bffe5825de7a2768a63bf29d39e0c1
diff --git a/.kitchen.yml b/.kitchen.yml
index e0554ba..574ca8a 100644
--- a/.kitchen.yml
+++ b/.kitchen.yml
@@ -31,7 +31,7 @@
 platforms:
   - name: <%=ENV['PLATFORM'] ||  'saltstack-ubuntu-xenial-salt-stable' %>
     driver_config:
-      image: <%=ENV['PLATFORM'] || 'epcim/salt-formulas:saltstack-ubuntu-xenial-salt-stable'%>
+      image: <%=ENV['PLATFORM'] || 'epcim/salt:saltstack-ubuntu-xenial-salt-stable'%>
       platform: ubuntu