fix(packaging): Require online network in systemd unit file for Loki and Promtail (#12741)

From https://systemd.io/NETWORK_ONLINE/:

**How do I make sure that my service starts after the network is really online?**

That depends on your setup and the services you plan to run after it (see above). If you need to delay you service after network connectivity has been established, include

```systemd
After=network-online.target
Wants=network-online.target
```

in the `.service` file.

This will delay boot until the network management software says the network is “up”. For details, see the next question.

Signed-off-by: Christian Haudum <christian.haudum@gmail.com>

tools/packaging/loki.service

@@ -1,6 +1,7 @@
 [Unit]
 Description=Loki service
-After=network.target
+After=network-online.target
+Wants=network-online.target
 
 [Service]
 Type=simple
@@ -12,4 +13,4 @@ Restart = on-failure
 RestartSec = 2
 
 [Install]
-WantedBy=multi-user.target
+WantedBy=multi-user.target

tools/packaging/promtail.service

@@ -1,6 +1,7 @@
 [Unit]
 Description=Promtail service
-After=network.target
+After=network-online.target
+Wants=network-online.target
 
 [Service]
 Type=simple
@@ -12,4 +13,4 @@ Restart = on-failure
 RestartSec = 2
 
 [Install]
-WantedBy=multi-user.target
+WantedBy=multi-user.target