Adding 6.x support with Bootstrap user addition

templates/systemd/elasticsearch.j2

@@ -7,6 +7,7 @@ After=network-online.target
 [Service]
 Environment=ES_HOME={{es_home}}
 Environment=CONF_DIR={{conf_dir}}
+Environment=ES_PATH_CONF={{conf_dir}}
 Environment=DATA_DIR={{ data_dirs | array_to_str }}
 Environment=LOG_DIR={{log_dir}}
 Environment=PID_DIR={{pid_dir}}
@@ -17,14 +18,18 @@ WorkingDirectory={{es_home}}
 User={{es_user}}
 Group={{es_group}}
 
+{% if (es_version | version_compare('6.0.0', '<')) %}
 ExecStartPre=/usr/share/elasticsearch/bin/elasticsearch-systemd-pre-exec
+{% endif %}
 
 ExecStart={{es_home}}/bin/elasticsearch \
                                     -p ${PID_DIR}/elasticsearch.pid \
-                                    --quiet \
+{% if (es_version | version_compare('6.0.0', '<')) %}
                                     -Edefault.path.logs=${LOG_DIR} \
                                     -Edefault.path.data=${DATA_DIR} \
-                                    -Edefault.path.conf=${CONF_DIR}
+                                    -Edefault.path.conf=${CONF_DIR} \
+{% endif %}
+                                    --quiet
 
 
 # StandardOutput is configured to redirect to journalctl since
@@ -41,9 +46,6 @@ StandardError=inherit
 LimitNOFILE={{es_max_open_files}}
 {% endif %}
 
-# Specifies the maximum number of processes
-LimitNPROC=2048
-
 # Specifies the maximum number of bytes of memory that may be locked into RAM
 # Set to "infinity" if you use the 'bootstrap.memory_lock: true' option
 # in elasticsearch.yml and 'MAX_LOCKED_MEMORY=unlimited' in {{instance_default_file}}