Removing the references of the elk stack

Because ELK stack isn't in the default playbooks anymore,
all the references to it should be removed from the
documentation section.

Change-Id: I5e79bc19cbb9070ece9b688d609303796ed0bef5

doc/source/install-guide/install-infrastructure.rst

@@ -18,20 +18,14 @@ services and performs the following operations:
 
 -  Install Memcached
 
+-  Install the repository server
+
 -  Install Galera
 
 -  Install RabbitMQ
 
 -  Install Rsyslog
 
--  Install Elasticsearch
-
--  Install Logstash
-
--  Install Kibana
-
--  Install Elasticsearch command-line utilities
-
 -  Configure Rsyslog
 
 --------------

doc/source/install-guide/overview-hostlayout.rst

@@ -41,6 +41,8 @@ services:
 
    -  Logging
 
+   -  Repository
+
 -  OpenStack:
 
    -  Identity (keystone)
@@ -59,10 +61,6 @@ Infrastructure Logging target hosts contain the following services:
 
 -  Rsyslog
 
--  Logstash
-
--  Elasticsearch with Kibana
-
 Compute target hosts contain the following services:
 
 -  Compute virtualization