Deduplicate handling of different error types returned from remote nodes.

[afck]

trafficstars

There are different places in the updater and client where we handle errors returned by remote nodes, e.g.:

• missing blobs published by the proposal,
• missing blobs used in the certificate,
• missing chain description blobs,
• missing events,
• missing incoming messages,
• wrong block height,
• wrong round.

In all these places we need to update the remote node and try again, which currently is done it some duplicated code.

We should try and create a single function (as far as possible) that maybe takes a closure, executes it, and on error updates the remote node and tries again.