Set RuntimeDirectory (#23526)

This instruction tells systemd to create a directory /var/run/elasticsearch before starting Elasticsearch.

Without this change, the default PID_DIR (/var/run/elasticsearch) may not exist, and without it, Elasticsearch will fail to start.

distribution/src/main/packaging/systemd/elasticsearch.service

@@ -5,6 +5,7 @@ Wants=network-online.target
 After=network-online.target
 
 [Service]
+RuntimeDirectory=elasticsearch
 Environment=ES_HOME=/usr/share/elasticsearch
 Environment=ES_PATH_CONF=${path.conf}
 Environment=PID_DIR=/var/run/elasticsearch