Fix SALT_FORMULAS_REFS block

Change-Id: Id5d4b7efdb6f56085b11926d572eb02e7d528fa2
Reviewed-on: https://review.gerrithub.io/374497
Reviewed-by: Dennis Dmitriev <dis.xcom@gmail.com>
Tested-by: Dennis Dmitriev <dis.xcom@gmail.com>
diff --git a/tcp_tests/templates/shared-salt.yaml b/tcp_tests/templates/shared-salt.yaml
index 5a563c7..0351418 100644
--- a/tcp_tests/templates/shared-salt.yaml
+++ b/tcp_tests/templates/shared-salt.yaml
@@ -273,7 +273,7 @@
     {%- for formula in SALT_FORMULAS_REFS.split(' ') %}
     {% set formula_name = formula.0 %}
     {% set formula_ref = formula.1 %}
-    {% set formula_dir = /tmp/salt-formula-{{ formula_name }} %}
+    {% set formula_dir = '/tmp/salt-formula-' + formula_name %}
     git clone {{ SALT_FORMULAS_REPO }}/{{ formula_name }} {{ formula_dir }} &&
     pushd {{ formula_dir }} &&
     git fetch {{ SALT_FORMULAS_REPO }}/{{ formula_name }} {{ formula_ref }} &&