Store and its lock file has been locked by another process: /var/lib/neo4j/data/databases/graph.db/store_lock

Killing the Java process and deleting the store_lock worked for me:

Found the lingering process,

ps aux | grep "org.neo4j.server"

killed it,

kill -9 <pid-of-neo4js-java-process>

and deleted

sudo rm /var/lib/neo4j/data/databases/graph.db/store_lock

Allegedly, just killing the lingering process may do the trick but I went ahead and deleted the lock anyway.

You can kill the java process and delete the store_lock file. It doesn't seem to harm the database integrity.