Fix messenger messages loss

[cedricfung]

The node has a in memory buffer to hold incoming and outgoing messages, so when the node panic, some messages may be lost. Thereafter, the messenger will not resend the messages, and all the nodes will retry the messages in one hour. The result is some signature may be lost and can only be retried after one hour.

Possible solution is to use some persistent cache, e.g. badger, to ensure messages processing.