make uploaders rotate the unique part of the key on failures (?)

[amwolff]

https://github.com/storj/common/blob/b9952c61d22febe124585cb2529231854d493a61/accesslogs/uploader.go#L197-L213:

…
if err := up.store.Put(context.TODO(), up.bucket, up.key, up.body); err != nil {
	if up.retries == u.retryLimit {
		mon.Event("upload_dropped")
		u.log.Error("retry limit reached",
			zap.String("bucket", up.bucket),
			zap.String("prefix", up.key),
			zap.Error(err),
		)
		if done := u.decrementQueueLen(closing); done {
			return nil
		}
		continue // NOTE(artur): here we could spill to disk or something
	}
	up.retries++
	u.queue <- up // failure; don't decrement u.queueLen
	mon.Event("upload_failed")
	continue
…

I saw failures when upload failing leads to the Storjuploader not being able to upload again because the access used might not have Delete capabilities (needed to overwrite the object). It's surprising this can happen, though, because if the upload fails, the key shouldn't exist with the current guarantees for atomicity.

The first step is to figure out if this is an expected behaviour.