The .lock file could still be present.
It seems that you really do not have another logstash running, you can confirm that with the following command:
ps -ef | grep logstash
If there is really not a logstash process running, remove the .lock file from the directory /var/lib/logstash.
Then configure your pipelines.yml file as following:
- pipeline.id: main
path.config: "/etc/logstash/logstash-its.conf"
After that start logstash using systemctl with systemctl start logstash.
Check the logs for any errors.