The int script does work, but only after you enable it in systemd (in disabled/bad state it doesn't use the sysv wrapper).
root@xenial-sandbox:~# systemctl enable elasticsearch
elasticsearch.service is not a native service, redirecting to systemd-sysv-install
Executing /lib/systemd/systemd-sysv-install enable elasticsearch
insserv: warning: current start runlevel(s) (empty) of scriptelasticsearch' overrides LSB defaults (2 3 4 5). insserv: warning: current stop runlevel(s) (0 1 2 3 4 5 6) of script
elasticsearch' overrides LSB defaults (0 1 6).
root@xenial-sandbox:~# systemctl start elasticsearch
root@xenial-sandbox:~# systemctl status elasticsearch
● elasticsearch.service - LSB: Starts elasticsearch
Loaded: loaded (/etc/init.d/elasticsearch; bad; vendor preset: enabled)
Active: active (running) since Thu 2016-05-26 10:26:36 CEST; 5s ago
Docs: man:systemd-sysv-generator(8)
Process: 1528 ExecStart=/etc/init.d/elasticsearch start (code=exited, status=0/SUCCESS)
Tasks: 29 (limit: 512)
Memory: 213.0M
CPU: 4.960s
CGroup: /system.slice/elasticsearch.service
└─1560 /usr/bin/java -Xms256m -Xmx1g -Djava.awt.headless=true -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:CMSInitiatingOccupancyFraction=75 -XX:+UseCMSInitiatingOccupancyOnly -XX:+HeapDumpOnOutOfMe
Edit: the 1.7.3 init script refuses to work, i copied the one from the 2.3.1 package, which does.
Edit2: just upgraded systemd to 229-4ubuntu6 and now both init scripts are "broken".