Rough upgrade from sysv to systemd initialization

When you upgrade from 0.26.5 to a higher version on a systemd-capable linux (ubuntu xenial tested), the upgrade doesn't stop old services, therefore new services will never start.

Expected Behavior

Upgrade happens automatically, with no manual intervention required. SystemV services are stopped before upgrade (maybe the correct behavior belongs to sensu project instead, and systemd setups would kill rogue processes before starting)

Current Behavior

Old processes linger, leaving systemd units in activating state:

root@luciuscornelius:~# ps -ef | grep sensu
root     13872 10932  0 08:55 pts/0    00:00:00 grep --color=auto sensu
sensu    22239     1  0 Mar14 ?        00:00:33 /opt/sensu/embedded/bin/ruby /opt/sensu/bin/sensu-client -b -c /etc/sensu/config.json -d /etc/sensu/conf.d -e /etc/sensu/extensions -p /var/run/sensu/sensu-client.pid -l /var/log/sensu/sensu-client.log -L info
root@luciuscornelius:~# less /var/log/sensu/sensu-client.log
root@luciuscornelius:~# systemctl status sensu-client
● sensu-client.service - sensu client
   Loaded: loaded (/etc/systemd/system/sensu-client.service; enabled; vendor preset: enabled)
   Active: activating (auto-restart) (Result: exit-code) since Wed 2017-03-15 08:55:11 CET; 43s ago
  Process: 13481 ExecStart=/opt/sensu/bin/sensu-service start client (code=exited, status=1/FAILURE)
 Main PID: 13481 (code=exited, status=1/FAILURE)

Mar 15 08:55:11 luciuscornelius systemd[1]: sensu-client.service: Unit entered failed state.
Mar 15 08:55:11 luciuscornelius systemd[1]: sensu-client.service: Failed with result 'exit-code'.
root@luciuscornelius:~# killall sensu-client
root@luciuscornelius:~# ps -ef | grep sensu
root     13895 10932  0 08:56 pts/0    00:00:00 grep --color=auto sensu
root@luciuscornelius:~# systemctl restart sensu-client
root@luciuscornelius:~# systemctl status sensu-client
● sensu-client.service - sensu client
   Loaded: loaded (/etc/systemd/system/sensu-client.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2017-03-15 08:56:16 CET; 8min ago
 Main PID: 13914 (sensu-client)
    Tasks: 24 (limit: 4915)
   Memory: 21.3M
      CPU: 630ms
   CGroup: /system.slice/sensu-client.service
           └─13914 /opt/sensu/embedded/bin/ruby /opt/sensu/bin/sensu-client -c /etc/sensu/config.json -d /etc/sensu/conf.d -e /etc/se

Mar 15 08:56:16 luciuscornelius systemd[1]: Started sensu client.

Possible Solution

I think of two possible resolutions of the problem:

stopping services before upgrade (package resource with notifies :before)
handling the issue outside of the recipe, reaping rogue processes before start in systemd unit file

Steps to Reproduce (for bugs)

take a systemd-enabled linux system
install 0.26.5-2
use cookbook to upgrade it to later versions

Your Environment

cookbook version: 4.0.0
Sensu version: 0.26.5-2 and 0.28.4-1
Chef version: 12.7.1 and higher
Operating System and version (e.g. CentOS 7, Ubuntu 14.04): ubuntu 16.04
Link to your project: I can share parts of my cookbook on request.

sensu / sensu-chef