Bucket.write() should retry non-resumable uploads too

[jonasfj]

As I've come to understand it there is some special code handling resumable uploads in googleapis package...

We should ensure that the same retry strategy is employed when doing non-resumable uploads in:
https://github.com/dart-lang/gcloud/blob/fbe7ef67f9234e2af00c18db6996c08f26a006ee/lib/src/storage_impl.dart#L595

[jonasfj]

After further investigation it seems things are not as simple, resumable uploads are only retried if it's not the first request initiating the resumable upload process.

Effectively, it seems retries are only attempted if uploading have been initiated..

I don't think we should fix this now, as there doesn't seem to be a clear policy on what we retry and when..