Add SyslogIdenfier to healthcheck systemd unit

Adding this new field will allow to filter all healthcheck logs using
the Idenfier value.

For instance, using journalctl, you would be able to run this:
`journalctl -t healthcheck_collectd'

It will also allow to get a dedicated file out of (r)syslog if needed.

This is the reflection of Icdc5caf4cedc46291a807c39c0a31c74955a4a74

Change-Id: I6861baa287f2a8288b87be26aacecbcc061cd96f
Closes-Bug: #1856573

paunch/utils/systemd.py

@@ -195,6 +195,7 @@ Requisite=%(service)s.service
 [Service]
 Type=oneshot
 ExecStart=/usr/bin/podman exec %(name)s %(test)s
+SyslogIdentifier=healthcheck_%(name)s
 [Install]
 WantedBy=multi-user.target
 """ % s_config)