Retry and attempt to recover from incremental send errors

When sending/receiving incremental snapshots results in the perennial
"cannot receive incremental stream: invalid backup stream" error, try
sending again. If it still fails, and the send covers a range of
snapshots, try sending each of them individually.

Every instance I've seen of this error will eventually succeed if
retried enough times, although this brute force approach can result in
sending vast amounts of duplicate data, so it might be worth
investigating a means of sending it once to a temporary file, confirming
a correct transfer, and just retrying the receive.