Don't send MsgAcknowledgment if channel is closed

[ancazamfir]

Crate

relayer

Summary of Bug

With a closed channel the MsgAcknowledgment will be rejected by the chain. Instead of sending (and retrying) it, the relayer should check the channel state on the destination chain and drop the message (there is no acknowledgment timeout on close or graceful channel shutdown procedure currently specified in IBC).

Version

Steps to Reproduce

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