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