split: copyOnce may be called more than once

[ignoramous]

Called twice when retrier.Write succeeds and returns immediately (L319) without waiting on <-retryCloseFlag (L324).

Intra/Android/app/src/go/intra/split/retrier.go

Lines 317 to 324 in 5c6d68d

	if attempted {
	if err == nil {
	return n, nil
	}
	// A write error occurred on the provisional socket. This should be handled
	// by the retry procedure. Block until we have a final socket (which will
	// already have replayed b[:n]), and retry.
	<-r.retryCompleteFlag

[jyyi1]

Thanks for the contribution!