Remove Salt deprecations and switch tests to Salt 2017.7

Change-Id: If96f95fdab13eae187a843f81b0d0060339a5f98
diff --git a/.kitchen.yml b/.kitchen.yml
index f3fc5b6..e708ea2 100644
--- a/.kitchen.yml
+++ b/.kitchen.yml
@@ -29,9 +29,9 @@
   sudo: true
 
 platforms:
-  - name: <%=ENV['PLATFORM'] || 'ubuntu-xenial'%>
+  - name: <%=ENV['PLATFORM'] || 'ubuntu-xenial-2017.7'%>
     driver_config:
-      image: <%=ENV['PLATFORM'] || 'trevorj/salty-whales:xenial'%>
+      image: <%=ENV['PLATFORM'] || 'trevorj/salty-whales:xenial-2017.7'%>
       platform: ubuntu