Make sure kitchen test dependencies formulas are always fetched from correct branch

Change-Id: Ic1f85f908eb399d9f01e3e6d20654ce3a86b9f1c
Related: PROD-29251
diff --git a/.kitchen.yml b/.kitchen.yml
index 83a7a4c..0d5450b 100644
--- a/.kitchen.yml
+++ b/.kitchen.yml
@@ -18,6 +18,7 @@
     - name: horizon
       repo: git
       source: https://github.com/salt-formulas/salt-formula-horizon
+      branch: <%=ENV['GERRIT_BRANCH'] || 'master' %>
   state_top:
     base:
       "*":