Suppress noisy notification in cloud

[patrickmann]

Fixes Graylog2/graylog-plugin-enterprise#8919

Description

See linked issue for details.

How Tested

• Launch a multi-node OS cluster in docker
• Find the node IDs by running docker ps
• Stop one of the nodes by running docker stop nodeID
• Observe that notification is triggered in master, but not in the fixed branch
• Observe that log message is output in fixed branch

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.