FEAT: paramaterize centos repos

• update group_vars to have variable for centos_repos
• update the related ansible playbook to pull from that variable

closes #257 (closed)

ansible/group_vars/all

@@ -89,3 +89,6 @@
   node_exporter_user: node_exporter
   node_exporter_group: node_exporter
   node_exporter_port: 9100
+
+# CentOS Repo
+  centos_base_url: "http://vault.centos.org"