Robustness: Tolerance for Temporary Failures

[carlaKC]

Right now we error-out on any LightningNode API failure. We should have some tolerance for temporary failures so that the simulation is more robust.

An example of the type of error we could hit: When LND starts up, GRPC calls will fail until it's unlocked its wallet and synced the chain.

[carlaKC]

Eg: @sr-gi pointed out that produce_events won't exit in the case of multiple producers for the same pair of channels.