Event monitor emits error when test framework shuts down the chains

[romac]

Summary of Bug

When the test framework shuts down the chains, the event monitor emits the following error:

2023-02-23T09:11:20.974583Z  INFO ibc_test_framework::types::binary::chains: stopping chain handle ibc-2
2023-02-23T09:11:20.974917Z  INFO ibc_test_framework::types::binary::chains: stopping chain handle ibc-1
2023-02-23T09:11:20.979464Z ERROR event_monitor{chain=ibc-1}: ibc_relayer::event::monitor: failed to collect events:
   0: WebSocket driver failed
   1:
   1:    0: web socket error: failed to read from WebSocket connection
   1:    1: WebSocket protocol error: Connection reset without closing handshake

This was introduced in 3095.

It is not a correctness problem and it does not impact the test results, but it clutters the logs and should be handled better.

Version

1.3.0

Steps to Reproduce

Run the integration test suite and look for the error above

Acceptance Criteria

The event monitor shuts down gracefully and does not emit errors.

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