Add packaging test for systemd runtime directive

We previously added a RuntimeDirectory directive to the systemd service
file for Elasticsearch. This commit adds a packaging test for the
situation that this directive was intended to address.

Relates #26229

qa/vagrant/src/test/resources/packaging/tests/60_systemd.bats

@@ -236,3 +236,13 @@ setup() {
     [ "$max_address_space" == "unlimited" ]
     systemctl stop elasticsearch.service
 }
+
+@test "[SYSTEMD] test runtime directory" {
+    clean_before_test
+    install_package
+    sudo rm -rf /var/run/elasticsearch
+    systemctl start elasticsearch.service
+    wait_for_elasticsearch_status
+    [ -d /var/run/elasticsearch ]
+    systemctl stop elasticsearch.service
+}