Upsert Doesn't Throw ObjectDisposedException

Most commands against CouchbaseBucket properly throw an ObjectDisposedException if called after the object is disposed.

However, Upsert commands do not. These commands just timeout instead. Upsert commands should be consistent with other commands in handling this invalid use case. This will make debugging issues simpler for the developer.

Note that this doesn't seem to affect UpsertAsync, just Upsert.