Issue #1200: Fix varnish role install on CentOS - latest role version.

Author: geerlingguy

provisioning/requirements.yml

@@ -76,4 +76,4 @@
 - src: geerlingguy.solr
   version: 3.5.1
 - src: geerlingguy.varnish
-  version: 1.8.1
+  version: 1.8.3

provisioning/roles/geerlingguy.varnish/README.md

@@ -82,7 +82,7 @@ None.
 *Inside `vars/main.yml`*:
 
     varnish_secret: "[secret generated by uuidgen]"
-    varnish_default_backend_host: 81
+    varnish_default_backend_port: 81
     ... etc ...
 
 ## License
@@ -91,4 +91,4 @@ MIT / BSD
 
 ## Author Information
 
-This role was created in 2014 by [Jeff Geerling](http://www.jeffgeerling.com/), author of [Ansible for DevOps](https://www.ansiblefordevops.com/).
+This role was created in 2014 by [Jeff Geerling](https://www.jeffgeerling.com/), author of [Ansible for DevOps](https://www.ansiblefordevops.com/).

provisioning/roles/geerlingguy.varnish/tasks/setup-RedHat.yml

@@ -5,6 +5,7 @@
     - gcc
     - libedit-devel
     - initscripts
+    - redhat-rpm-config
 
 - name: Add Varnish repository.
   yum: