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

Change-Id: I8d217b1d024a2af89d0daa0607ee9017fa95fd2b
Related: PROD-29251
diff --git a/.kitchen.yml b/.kitchen.yml
index 39f401f..47966af 100644
--- a/.kitchen.yml
+++ b/.kitchen.yml
@@ -18,12 +18,15 @@
     - name: linux
       repo: git
       source: https://gerrit.mcp.mirantis.com/salt-formulas/linux
+      branch: <%=ENV['GERRIT_BRANCH'] || 'master' %>
     - name: keystone
       repo: git
       source: https://gerrit.mcp.mirantis.com/salt-formulas/keystone
+      branch: <%=ENV['GERRIT_BRANCH'] || 'master' %>
     - name: oslo_templates
       repo: git
       source: https://gerrit.mcp.mirantis.com/salt-formulas/oslo-templates
+      branch: <%=ENV['GERRIT_BRANCH'] || 'master' %>
   state_top:
     base:
       "*":