Gemfile in chef-dk-0.18.30

- old
+ new

@@ -10,5 +10,8 @@
 gem "winrm-elevated"
 gem "berkshelf"
 
 # TODO remove this when we update Chef to use the new api exposed in 3.5.1
 gem "rspec-core", "= 3.4.4"
+
+# until 2.0.0 is fixed for unstable packages
+gem "mixlib-install", "1.2.3"