Remove multi instances support (#566)

* remove multi instances support
The goal is to stop supporting installation of more than one node in the same host. This commit update the Ansible role README documentation and remove the multi instances kitchen test.

* remove systemd and init.d templates
As we no more need to support more than one node on the same host, we no more need to override init files provided by elasticsearch official packages.

* remove file script feature
File scripts have been removed since elasticsearch 6.0 (https://www.elastic.co/guide/en/elasticsearch/reference/6.0/breaking_60_scripting_changes.html#_file_scripts_removed)

* remove custom user and custom group
ES_USER and ES_GROUP settings are no longer supported (https://www.elastic.co/guide/en/elasticsearch/reference/6.0/breaking_60_packaging_changes.html#_configuring_custom_user_and_group_for_package_is_no_longer_allowed)

* add upgrade procedure

* use same task for license activation with and without authentication

tasks/elasticsearch-parameters.yml

@@ -1,9 +1,5 @@
 # Check for mandatory parameters
 
-- name: fail when es_instance is not defined
-  fail: msg="es_instance_name must be specified and cannot be blank"
-  when: es_instance_name is not defined or es_instance_name == ''
-
 - name: fail when es_proxy_port is not defined or is blank
   fail: msg="es_proxy_port must be specified and cannot be blank when es_proxy_host is defined"
   when: (es_proxy_port is not defined or es_proxy_port == '') and (es_proxy_host is defined and es_proxy_host != '')
@@ -34,38 +30,5 @@
      msg: "ERROR: INVALID CONFIG - YOU CANNOT CHANGE RESERVED USERS THROUGH THE FILE REALM. THE FOLLOWING CANNOT BE CHANGED: {{file_reserved_users}}. USE THE NATIVE REALM."
   when: file_reserved_users | default([]) | length > 0
 
-- name: set fact instance_default_file
-  set_fact: instance_default_file={{default_file | dirname}}/{{es_instance_name}}_{{default_file | basename}}
-- name: set fact instance_init_script
-  set_fact: instance_init_script={{init_script | dirname }}/{{es_instance_name}}_{{init_script | basename}}
-- name: set fact conf_dir
-  set_fact: conf_dir={{ es_conf_dir }}/{{es_instance_name}}
 - name: set fact m_lock_enabled
   set_fact: m_lock_enabled={{ es_config['bootstrap.memory_lock'] is defined and es_config['bootstrap.memory_lock'] == True }}
-
-#TODO - if transport.host is not local maybe error on boostrap checks
-
-
-#Use systemd for the following distributions:
-#Ubuntu 15 and up
-#Debian 8 and up
-#Centos 7 and up
-#Relies on elasticsearch distribution installing a serviced script to determine whether one should be copied.
-
-- name: set fact use_system_d
-  set_fact: use_system_d={{(ansible_distribution == 'Debian' and ansible_distribution_version is version_compare('8', '>=')) or (ansible_distribution in ['RedHat','CentOS'] and ansible_distribution_version is version_compare('7', '>=')) or (ansible_distribution == 'Ubuntu' and ansible_distribution_version is version_compare('15', '>=')) }}
-
-- name: set fact instance_sysd_script
-  set_fact: instance_sysd_script={{sysd_script | dirname }}/{{es_instance_name}}_{{sysd_script | basename}}
-  when: use_system_d
-#For directories we also use the {{inventory_hostname}}-{{ es_instance_name }} - this helps if we have a shared SAN.
-
-- name: set fact instance_suffix
-  set_fact:
-    instance_suffix: "{{ es_instance_suffix | default([inventory_hostname, es_instance_name] | join('-')) }}"
-- name: set fact pid_dir
-  set_fact: pid_dir={{ es_pid_dir }}/{{instance_suffix}}
-- name: set fact log_dir
-  set_fact: log_dir={{ es_log_dir }}/{{instance_suffix}}
-- name: set fact data_dirs
-  set_fact: data_dirs={{ es_data_dirs | append_to_list('/'+instance_suffix) }}