Fully sync single-owner chains if necessary.

[afck]

The client currently assumes that if a chain has only one owner, then the current wallet is the only one used to interact with the chain, and is always up-to-date. So it skips the chain info request to the validators to find out whether there are any new blocks on the chain that it doesn't know about.

But this assumption is not always true; e.g. a restored backup wallet may be out of date, and in some cases users do use the same key with multiple wallets.

We should either remove the optimization (it's only one round-trip to get a small chain info response), or (maybe better) do the full synchronization if a block proposal fails because the validators have more blocks.