Fix Ansible 2.3.0.0 deprecation bug

tasks/install.yml

@@ -55,7 +55,7 @@
 - block:
   - set_fact: drupal_first_installation=false
   - set_fact: drupal_first_installation=true
-    when: drupal_install_drupal and drupal_available is defined and drupal_available.stdout != '{{ drupalRoot }}/index.php'
+    when: drupal_install_drupal and drupal_available is defined and drupal_available.stdout != [drupalRoot, '/index.php']|join('')
   tags: always
 
 - include: install/{{ installSource.mode|default("none") }}.yml