Ensure Neo4j save operations are only executed in main thread

[davidkopp]

Neo4j has problems with multiple deadlocks. For more information read the official documentation about transactions-locking.

We encountered the problem e.g. by executing the integration test DeploymentResourceIntegrationTests.deployApplicationWithMultipleKafkaFaasConnectorInstances with the Neo4j Embedded Database. With a local Neo4j database running with Docker it works.

Nevertheless it would be safer to avoid save operations in worker threads -> if possible only use the main thread.