`gcloud.aio.storage.blob.Blob.update` corrupts the `Blob` object

[aucampia]

When uploading, the blob object's bucket attribute changes from a value of type gcloud.aio.storage.Bucket to str as it is overwritten by the string returned from GCP:

gcloud-aio/storage/gcloud/aio/storage/blob.py

Line 123 in 75046bf

self.__dict__.update(metadata)