Enabled workaround condition for blackfire repo

Author: mblaschke

docker/main/centos/provision/roles/php/tasks/blackfire.yml

@@ -14,7 +14,7 @@
     dest:   /etc/yum.repos.d/blackfire.repo
     regexp: '^repo_gpgcheck=1'
     line:   'repo_gpgcheck=0'
-#  when: ansible_distribution == 'CentOS' and ansible_distribution_version == "7"
+  when: ansible_distribution == 'CentOS' and ansible_distribution_major_version == '7'
 
 - name: Install blackfire-php
   yum: