Run some tests just if plugin is installed.

When having different branches, with different plugins, some branches test different plugins that other ones.

I wanted the same CI to select dynamically different test case scenarios.
To keep compatibility some conditional has to be added.

docker-compose.yml

@@ -14,7 +14,7 @@ services:
             start_period: 60s
             start_interval: 5s
             retries: 5
-            test: "curl -f http://localhost:8080/api/ || exit 1"
+            test: "curl -f http://localhost:8080 || exit 1"
         env_file: env/netbox.env
         volumes:
             - netbox-media-files:/opt/netbox/netbox/media