Improve backoff/retry when user does not have permission to access bucket

Suggested Release Note:

Reduced the rate at which messages appear in the server's `http_access.log` when valid credentials are provided, but the user does not have permission to access the bucket.

An SDK configured with credentials for a user who does not have access to the bucket spams the server with HTTP requests for "/pools/default/b/<bucket-name>". It would be nice to throttle these requests somehow.

To reproduce:

• Create two buckets, "a" and "b".
• Create a user and assign "Data Reader" (not "Bucket Admin"!) access for bucket "a".

public static void main(String... args) throws Exception {

  Cluster cluster = Cluster.connect("127.0.0.1", username, password);

  Bucket bucket = cluster.bucket("b"); // user has no permission for this bucket

  MINUTES.sleep(10);

}

and tail var/lib/couchbase/logs/http_access.log