Ignore whitespace at periodic flag

We were going to always evaluate it to false, there were a whitespace
after expanding the jinja template.

Change-Id: I37f9f8a99584fcbdfc5f937baf755eb12045e18e

playbooks/tripleo-ci/vars/common.yaml

@@ -14,7 +14,7 @@ featureset_conf: >-
 periodic: >-
   {% if 'periodic' in zuul.pipeline -%}
   true
-  {% else %}
+  {%- else -%}
   false
   {%- endif %}