STORAGE: Does a connection need to be bound to anything other than a Batch or Iterator?

Run

```
$ git grep -n '\.connection' -- gcloud/datastore/ | egrep -v test | egrep -v 'datastore\.connection'
$ git grep -n '\.connection' -- gcloud/storage/ | egrep -v test | egrep -v 'storage\.connection'
```

to compare uses.
