Apache servers will not reporting version anymore

In order to make it more difficult to know which
httpd server is running, here is a change to 
reduce the ServerTokens OS to ServerTokens Prod
and the ServerSignature On to ServerSignature Off.

This removes ServerName and version report
on page footer and reduces the detail of the httpd
server running in the headers to "Apache". 

These options can be overwritten by an user variable

Change-Id: I1aaffaa3b6b7d6574aefac65b6027e62240a702b
Closes-Bug: #1484256

defaults/main.yml

@@ -49,6 +49,8 @@ horizon_lib_dir: /usr/local/lib/python2.7/dist-packages
 horizon_endpoint_type: internalURL
 
 horizon_server_name: "horizon"
+horizon_apache_servertokens: "Prod"
+horizon_apache_serversignature: "Off"
 horizon_log_level: info
 horizon_dropdown_max_items: 30
 horizon_time_zone: UTC

tasks/horizon_apache.yml

@@ -63,3 +63,21 @@
   notify: Restart apache2
   tags:
     - horizon-apache-config
+
+- name: Ensure Apache ServerTokens
+  lineinfile:
+    dest: "/etc/apache2/conf-available/security.conf"
+    regexp: '^ServerTokens'
+    line: "ServerTokens {{ horizon_apache_servertokens }}"
+  notify: Restart apache2
+  tags:
+    - horizon-apache-config
+
+- name: Ensure Apache ServerSignature
+  lineinfile:
+    dest: "/etc/apache2/conf-available/security.conf"
+    regexp: '^ServerSignature'
+    line: "ServerSignature {{ horizon_apache_serversignature }}"
+  notify: Restart apache2
+  tags:
+    - horizon-apache-config