[tunnelbroker] Ignore connection error messages handled elsewhere

Summary:
This is to avoid alerting spam for errors from inside lapin library that we handle e.g. by reconnecting to RabbitMQ.

Depends on D13607

Test Plan:
When Tunnelbroker is open, stop RabbitMQ server.

Before: Error was displayed with errorType = AMQP_ERROR that connection is lost.
After: The error is not displayed from this handler. Error message appears only when all exponential backoff attempts fail.

Reviewers: kamil, varun, will

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13608