PHP FPM will now notify systemd when it's done initializing and ready to
serve requests.
Additionally ```systemctl status phpfpm``` will now show statistics such
as:
```
Status: "Processes active: 0, idle: 8, Requests: 0, slow: 0, Traffic: 0req/sec"
```
From @fpletz: Keep poolConfigs option for backwards-compatibility.
The original commit 6b3f5b5a42 was previously
reverted by c7860cae1a but the issues were
resolved.
This reverts commit 6b3f5b5a42 because it
introduced a non-backwards compatible change in the phpfpm interface,
without really needing to. The new interface, if needed, can be re-added
alongside the old interface.
Commit 98e419c0e2 ("tt-rss service: init at 16.3")
depends on the new interface, so this commit updates the tt-rss service
to work with the old services.phpfpm.poolConfigs interface.
