Replace 'service mysql reload' with
'systemctl restart mysql' in MySQL upgrade pipeline

In version 5.7 of MySQL file /etc/init.d/mysql
is missing so reload command doesn’t work. Systemd used instead

PROD-36756

Change-Id: I96fe4a0125efae8413def4a64fa67b5106de3d16
diff --git a/openstack-galera-upgrade.groovy b/openstack-galera-upgrade.groovy
index 64dbbad..1f8d601 100644
--- a/openstack-galera-upgrade.groovy
+++ b/openstack-galera-upgrade.groovy
@@ -180,7 +180,7 @@
 
     if (shutdownCluster) {
       openstack.runOpenStackUpgradePhase(env, masterNode, 'render_config')
-      salt.cmdRun(env, masterNode, "service mysql reload")
+      salt.cmdRun(env, masterNode, "systemctl restart mysql")
       openstack.runOpenStackUpgradePhase(env, masterNode, 'verify')
     }