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

Change-Id: I5cd15fd9db76bfd60c82bf1d5d2ff57529b8b70b
Related: PROD-29251
diff --git a/.kitchen.yml b/.kitchen.yml
index 2e6b8d6..97768e8 100644
--- a/.kitchen.yml
+++ b/.kitchen.yml
@@ -18,6 +18,7 @@
     - name: linux
       repo: git
       source: https://github.com/salt-formulas/salt-formula-linux
+      branch: <%=ENV['GERRIT_BRANCH'] || 'master' %>
   state_top:
     base:
       "*":